Switched layer management to use a QTableView. Layer management is now similar to how it is in Photoshop and not a tree.
Merge commit '5abe0ce' into layertable
Started work on allowing layers to be reordered via drag and drop
Removing work done on allowing drag and drop in layer manager. No facility exists for changing draw order. Maybe in the future.
Merge commit '4431d81' into layertable
Started removing requirement for MAIN_LAYER
Add checkbox to toggle layer visibility
Merge commit '5276e80' into layertable
Merge branch 'R38' into layertable
Cleaned up hide/show layer functionality.
Remove more traces of MAIN_LAYER. Update TODO tasks so Eclipse will pick them up (can't add name.)
Merge branch 'R38' into layertable

Conflicts:
	PythonCAD/Interface/idocument.py
Merge branch 'R38' into layertable