FEM: scripting FEM module without the need of adding document objects

Issue imported from https://tracker.freecad.org/view.php?id=3055

* **Reporter:** berndhahnebach
* **Date submitted:** 5/27/2017
* **FreeCAD version:** 0.17
* **Category:** Feature
* **Status:** confirmed
* **Tags:** python

# Original report text

If one would like to script with FEM he ***has to*** add document object for each instance he would work with. If one works with Shapes or Meshes or FEMMeshes one ***does not*** need to add a document object for each instance he would work with.

The original idea was from ickby. I didn't even know what he was talking about when he came up with it but he explained it and YEAH we sure need it. If you get it it is just obvious we need this !

Ahh Forum posts:
https://forum.freecadweb.org/viewtopic.php?f=18&t=16944#p134521
https://forum.freecadweb.org/viewtopic.php?f=18&t=16944&start=10#p134582

# Other bug information

* **Priority:** normal
* **Severity:** feature
* **Category:** Feature
* **Updated:** 2/6/2021