Fix various typos [skip ci]

Fixed 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/AddonManager/Resources/icons/Manipulator_workbench_icon.svg

@@ -380,7 +380,7 @@
             <rdf:li>cross</rdf:li>
           </rdf:Bag>
         </dc:subject>
-        <dc:description>Four equally sized arrow heads at 90° to eachother, all joined at the tail</dc:description>
+        <dc:description>Four equally sized arrow heads at 90° to each other, all joined at the tail</dc:description>
       </cc:Work>
     </rdf:RDF>
   </metadata>

src/Mod/Mesh/App/Core/Iterator.h

@@ -340,7 +340,7 @@ inline void MeshFacetIterator::Transform( const Base::Matrix4D& rclTrf )
 {
   _clTrf = rclTrf;
   Base::Matrix4D tmp;
-  // cecks for unit matrix
+  // checks for unit matrix
   _clTrf != tmp ? _bApply = true : _bApply = false;
 }
 
@@ -438,7 +438,7 @@ inline void MeshPointIterator::Transform( const Base::Matrix4D& rclTrf )
 {
   _clTrf = rclTrf;
   Base::Matrix4D tmp;
-  // cecks for unit matrix
+  // checks for unit matrix
   _clTrf != tmp ? _bApply = true : _bApply = false;
 }
 

src/Mod/MeshPart/App/AppMeshPartPy.cpp

@@ -134,8 +134,8 @@ public:
             "    MinLength (required, float)\n"
             "    Fineness (required, integer)\n"
             "    SecondOrder (optional, integral boolean)\n"
-            "    Optimize (optional, integeral boolean)\n"
-            "    AllowQuad (optional, integeral boolean)\n"
+            "    Optimize (optional, integral boolean)\n"
+            "    AllowQuad (optional, integral boolean)\n"
             "    GrowthRate (optional, float)\n"
             "    SegPerEdge (optional, float)\n"
             "    SegPerRadius (optional, float)\n"

src/Mod/Path/Tools/README.md

@@ -64,7 +64,7 @@ TechDraw's templates.
 
 ## How to create a new tool bit Shape
 
-A tool bit template represents the physical shape of a tool. It does not completely desribe the bit - for that some
+A tool bit template represents the physical shape of a tool. It does not completely describe the bit - for that some
 additional parameters are needed which will be added when an actual bit is parametrized from the template.
 
 1. Create a new FreeCAD document

src/Mod/Sandbox/exportDRAWEXE.py

@@ -161,7 +161,7 @@ def saveShape(csg,filename,shape,name,hasplacement = True,cleanshape=False):
         sh=shape.copy()
         sh.Placement=FreeCAD.Placement()
         # it not yet tested if changing the placement recreated the
-        # tessellation. but for now we simply do the cleaing once again
+        # tessellation. But for now we simply do the cleaning once again
         # to stay on the safe side
         if cleanshape:
             shape = shape.cleaned()