Fix typos and misc. formatting [skip ci]

Found via `codespell -q 3 -L aci,ake,aline,alle,alledges,alocation,als,ang,anid,ba,beginn,behaviour,bloaded,byteorder,calculater,cancelled,cancelling,cas,cascade,centimetre,childs,colour,colours,commen,currenty,dof,doubleclick,dum,eiter,elemente,feld,freez,hist,iff,indicies,initialisation,initialise,initialised,initialises,initialisiert,ist,kilometre,lod,mantatory,methode,metres,millimetre,modell,nd,noe,normale,normaly,nto,numer,oder,orgin,orginx,orginy,ot,pard,pres,programm,que,recurrance,rougly,seperator,serie,sinc,strack,substraction,te,thist,thru,tread,uint,unter,vertexes,wallthickness,whitespaces -S ./.git,*.po,*.ts,./ChangeLog.txt,./src/3rdParty,./src/Mod/Assembly/App/opendcm,./src/CXX,./src/zipios++,./src/Base/swig*,./src/Mod/Robot/App/kdl_cp,./src/Mod/Import/App/SCL,./src/WindowsInstaller,./src/Doc/FreeCAD.uml`

src/Mod/Fem/App/FemAnalysis.h

@@ -45,7 +45,7 @@ namespace Fem {
  *  compatibility handling via handleChangedPropertyName.
  *
  *  This implies that it is not checked which objects are put into the
- *  Analsis object. Every document object of FreeCAD can be part of a
+ *  Analysis object. Every document object of FreeCAD can be part of a
  *  Analysis.
  */
 class AppFemExport FemAnalysis : public App::DocumentObjectGroup {

src/Mod/Fem/App/FemConstraintFluidBoundary.cpp

@@ -70,7 +70,7 @@ ConstraintFluidBoundary::ConstraintFluidBoundary()
                       "Basic boundary type like inlet, wall, outlet,etc");
     BoundaryType.setEnums(BoundaryTypes);
     ADD_PROPERTY_TYPE(Subtype,(1),"FluidBoundary",(App::PropertyType)(App::Prop_None),
-                      "Subtype defines more specific boudnary types");
+                      "Subtype defines more specific boundary types");
     Subtype.setEnums(WallSubtypes);
     ADD_PROPERTY_TYPE(BoundaryValue,(0.0),"FluidBoundary",(App::PropertyType)(App::Prop_None),
                       "Scaler value for the specific value subtype, like pressure, velocity magnitude");

src/Mod/Fem/App/FemResultObject.cpp

@@ -41,7 +41,7 @@ FemResultObject::FemResultObject()
     ADD_PROPERTY_TYPE(Mesh,(0), "General",Prop_None,"Link to the corresponding mesh");
     ADD_PROPERTY_TYPE(NodeNumbers,(0), "NodeData",Prop_None,"Numbers of the result nodes");
     ADD_PROPERTY_TYPE(Stats,(0), "Data",Prop_None,"Statistics of the results");
-    ADD_PROPERTY_TYPE(Time,(0), "Data",Prop_None,"Time of analysis incement");
+    ADD_PROPERTY_TYPE(Time,(0), "Data",Prop_None,"Time of analysis increment");
 
     // make read-only for property editor
     NodeNumbers.setStatus(App::Property::ReadOnly, true);

src/Mod/Fem/coding_conventions.md

@@ -1,17 +1,24 @@
 # FEM coding_conventions
-- These coding rules apply to FEM module code only. Other modules or the base system may use different coding rules especially in naming policy of Python.
-
+These coding rules apply to FEM module code only. Other modules or the base system may use different coding rules especially in naming policy of Python.
 
 ## Spelling
 - Be mindful of spelling. Spell checks are quite often neglected.
-- [codespell]((https://github.com/codespell-project/codespell#updating) could be used  
+- Utilize [codespell](https://github.com/codespell-project/codespell) to discover and quickly correct spelling errors.  
 
-~~~
-codespell -q 2 -S *.ts  -L childs,dof,dum,methode,nd,normaly,uint,vertexes,freez  src/Mod/Fem/
-~~~
+  ```bash
+  # Find typos
+  codespell -q 2 -S *.ts -L childs,dof,dum,methode,nd,normaly,uint,vertexes,freez src/Mod/Fem/
+  # Interactively fix said typos
+  codespell -i 3 -w -S *.ts -L childs,dof,dum,methode,nd,normaly,uint,vertexes,freez src/Mod/Fem/
+  ```
+
+  **Notes:**  
+  1) We recommend running the dev version as it uses the most up to date typo dictionaries.  
+  2) To find the most amount of typos we recommend running a quick `pip install --upgrade`  
+  See the [codespell docs](https://github.com/codespell-project/codespell#updating) for more info.
 
 ## Python and C++
-#### Code formatting
+### Code formatting
 - All files should have a license header
 - Unix line endings are preferred
 - never use mixed line endings on one file
@@ -20,7 +27,7 @@ codespell -q 2 -S *.ts  -L childs,dof,dum,methode,nd,normaly,uint,vertexes,freez
 
 
 ## Python
-#### Code formatting
+### Code formatting
 - except W503 all Python code is pep8 compliant
 - maximal line length is 100
 - double quotes as string identifier
@@ -31,32 +38,29 @@ codespell -q 2 -S *.ts  -L childs,dof,dum,methode,nd,normaly,uint,vertexes,freez
 - snake_case_names
 - ClassNames, variable_names_without_capitals and CONSTANTS_USE_CAPITALS, functions_without_capitals
 - Function expected to return a value should indicate what is expected, so is_mesh_valid is a good name, but check_mesh is not a good name
-- Class names, methode names and variable that are locally and not supposed to be used for scripting should start with underscore like _MyInternalClass
+- Class names, method names and variable that are locally and not supposed to be used for scripting should start with underscore like _MyInternalClass
 
 ### Python code formatting tools
-- flake8
-    - in source code directory on Linux shell
-~~~
+- **flake8** in source code directory on Linux shell
+```bash
 find src/Mod/Fem/ -name "*\.py" | grep -v InitGui.py | xargs -I [] flake8 --ignore=E266,W503 --max-line-length=100 []
-~~~
-
+```
 - [LGTM](www.lgtm.com)
 - TODO: check pylint
-- automatic code formatter will not be used for existent code
-- for new code if someone would like to use a code formatter black should be used
+- Automatic code formatter will not be used for existent code
+- For new code if someone would like to use a code formatter black should be used
 
 ### Coding
 - print() vs. FreeCAD.Console.PrintMessage()
-    - FreeCAD.Console.PrintMessage() or Log or Error should be used
-    - print() should be used for debugging only
-    - forum topic https://forum.freecadweb.org/viewtopic.php?f=10&t=39110
-    - BTW: Console prints need a new line where as print does not need one
+  - `FreeCAD.Console.PrintMessage()` or Log or Error should be used
+  - `print()` should be used for debugging only
+  - [forum topic](https://forum.freecadweb.org/viewtopic.php?f=10&t=39110) 
+  - BTW: Console prints need a new line where as print does not need one
 
 ### Documenting
-- Python style is preferred over Doxygen style
-    - see ccx tools module in fem tools package
-    - see forum topic: https://forum.freecadweb.org/viewtopic.php?f=10&t=37094
-
+Python style is preferred over Doxygen style
+  - see `ccx` tools module in fem tools package
+  - see [forum topic](https://forum.freecadweb.org/viewtopic.php?f=10&t=37094)
 
 ## C++
 ### Naming policy

src/Mod/Fem/femsolver/elmer/writer.py

@@ -482,7 +482,7 @@ class Writer(object):
                 dimension = "M/L^3"
                 if name.startswith("Edge"):
                     # not tested, but it seems needed
-                    # because denisty does not exist (IMHO, bernd)
+                    # because density does not exist (IMHO, bernd)
                     density = None
                     if density:
                         density.Unit = Units.Unit(-2, 1)

src/Mod/Fem/femsolver/settings.py

@@ -34,7 +34,7 @@ are supported:
     - ElmerSolver
     - Z88
 
-To query settings about those solver the solver name must be given exactely in
+To query settings about those solver the solver name must be given exactly in
 the form written in the list above. To make the solver recognize settings for a
 new solver have a look at :class:`_SolverDlg`.
 """

src/Mod/Fem/femtools/femutils.py

@@ -195,7 +195,7 @@ def get_mesh_to_solve(analysis):
 
     :returns:
      A tuple ``(object, message)``. If and only if the analysis contains
-     exactely one mesh object the first value of the tuple is the mesh document
+     exactly one mesh object the first value of the tuple is the mesh document
      object. Otherwise the first value is ``None`` and the second value is a
      error message indicating what went wrong.
     """
@@ -235,7 +235,7 @@ def is_of_type(obj, ty):
 
     :returns:
      ``True`` if *obj* is of type *ty*, ``False`` otherwise. Type must match
-     exactely: Derived objects are not considered to be of type of one of their
+     exactly: Derived objects are not considered to be of type of one of their
      super classes.
     """
     return type_of_obj(obj) == ty