* [Part] feature to make persistent section cut views
* one aim is to have a feature to make real cuts, not hollow ones like with clipping
* the second one is to have a persistent view, so an object in the tree that can be further exported, meshed etc.
For a detailed description with examples see https://forum.freecadweb.org/viewtopic.php?f=17&t=52441
This PR adds the same functionality as provided by Part Extrude.
The used code parts are sorted out to a new helper function that is used by Part and PartDesign.
- there can be strange cases with structures all intersecting each other. Their extrusion has no practical use case but we must avoid that such structures results either in an infinite loop or in an invalid geometric result.
Found via `codespell -q 3 -L aci,ake,aline,alle,alledges,alocation,als,ang,anid,apoints,ba,beginn,behaviour,bloaded,bottome,byteorder,calculater,cancelled,cancelling,cas,cascade,centimetre,childrens,childs,colour,colours,commen,connexion,currenty,dof,doubleclick,dum,eiter,elemente,ende,feld,finde,findf,freez,hist,iff,indicies,initialisation,initialise,initialised,initialises,initialisiert,inout,ist,kilometre,lod,mantatory,methode,metres,millimetre,modell,nd,noe,normale,normaly,nto,numer,oce,oder,ontop,orgin,orginx,orginy,ot,pard,parm,parms,pres,programm,que,rady,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,./build/doc/SourceDocu`