Fix various (doxy) typos and whitespace issues

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/FemConstraint.h

@@ -36,7 +36,7 @@ namespace Fem {
  * @brief Base class of all Constraint Objects of the Fem module.
  *
  * @details
- *  @ref Constraint isn't intended to be used directely. Actual Constraints
+ *  @ref Constraint isn't intended to be used directly. Actual Constraints
  *  used to specify a simulation are children of this class. The base class
  *  essentially does two things: Most importantely it has a property @ref
  *  Constraint::References which is a list of all sub objects the constraint
@@ -185,7 +185,7 @@ protected:
      *  index in normals[i].
      *
      * @param[out] points
-     *  For each vertex a point equal to the location of that vertix is pushed
+     *  For each vertex a point equal to the location of that vertex is pushed
      *  into the points vector. For each edge at least to points, the beginning
      *  and the end of the edge, are pushed into the vector. Depending on the
      *  length of the edge more points may be added in between. For each face a

src/Mod/Fem/Gui/Command.cpp

@@ -1489,7 +1489,7 @@ void CmdFemPostFunctions::activated(int iMsg)
             qApp->translate("CmdFemPostClipFilter", "Select a pipeline, please."));
     }
 
-    // Since the default icon is reset when enabing/disabling the command we have
+    // Since the default icon is reset when enabling/disabling the command we have
     // to explicitly set the icon of the used command.
     Gui::ActionGroup* pcAction = qobject_cast<Gui::ActionGroup*>(_pcAction);
     QList<QAction*> a = pcAction->actions();

src/Mod/Fem/femsolver/run.py

@@ -74,7 +74,7 @@ def run_fem_solver(solver, working_dir=None):
         A document object which must be a framework compliant solver. This means
         that it should be derived from the document object provided by
         :mod:`femsolver.solverbase` and implement all required methods
-        correctely. Of particular importance is :meth:`getMachine
+        correctly. Of particular importance is :meth:`getMachine
         <femsolver.solverbase.Proxy.getMachine>` as it is used by this method
         the get the :class:`Machine` used to execute the solver.
 
@@ -154,7 +154,7 @@ def getMachine(solver, path=None):
         A document object which must be a framework compliant solver. This means
         that it should be derived from the document object provided by
         :mod:`femsolver.solverbase` and implement all required methods
-        correctely. Of particular importance is :meth:`getMachine
+        correctly. Of particular importance is :meth:`getMachine
         <femsolver.solverbase.Proxy.getMachine>` as it is used by this method
         to create a new :class:`Machine` on cache miss.
 

src/Mod/Fem/femtools/femutils.py

@@ -268,7 +268,7 @@ def get_pref_working_dir(solver_obj):
      If user setting is set to BESIDE and the document isn't saved.
 
     :note:
-     Not working correctely for most cases because this circumvents directory
+     Not working correctly for most cases because this circumvents directory
      caching of the solver framework. For solver use getMachine from run.py
      instead.
     """