* Better module import error handling
* Allow co-installation of Python2 and Python3 version of FreeCAD
* Add FreeCAD.Logger class for convenient logging in Python. See class
document for more details.
See bug description:
https://bitbucket.org/Coin3D/coin/pull-requests/119/fix-sochildlist-auditing/diff
Because of path based rendering (SoFCPathAnnotation) in mouse over
highlight, this bug causes crash more frequently here comparing to
upstream.
All C++ calling of SoGroup::removeAllChildren() is replaced by
Gui::coinRemoveAllChildren(), and python code is fixed by monkey
patching SoGroup.removeAllChildren() in FreeCADGuiInit.py.
(this mostly aims at new modules and extension modules which want to use pip)
- any module having problems with nameclashes can use this syntax (from freecad import module)
- current imports still work (backward cobatibility)
- python extension moduels can be installed (pip) to python std path (eg.: site-packages)
- adding app, gui to the new freecad package:
```
from freecad import app
from freecad import gui
```
- syntax for importing c++ extension will not change
```
import FreeCAD as App
import FreeCADGui as Gui
```
