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/App/ApplicationPy.cpp

@@ -119,7 +119,7 @@ PyMethodDef Application::Methods[] = {
      "newDocument(name, label=None, hidden=False) -> object\n"
      "Create a new document with a given name.\n\n"
      "name: unique document name which is checked automatically.\n"
-     "label: optional user changable label for the document.\n"
+     "label: optional user changeable label for the document.\n"
      "hidden: whether to hide document 3D view."},
     {"closeDocument",  (PyCFunction) Application::sCloseDocument, METH_VARARGS,
      "closeDocument(string) -> None\n\n"