* [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
bb204842f2