Draft: gui_trackers clean up docstrings and spaces (3)
Draft: gui_trackers clean up docstrings and spaces (3)

Many small spacing fixes in the code, to improve the Pythonic
style according to PEP8.
Also add many docstrings in triple quotes.

Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master