Adding simple mouse interaction to ViewBox + TwoDCamera
a bit closer
fixed entity_transform method
Mouse interaction working for TwoDCamera
Merge branch 'scenegraph' into mouse_interaction

Conflicts:
	vispy/scene/cameras.py
	vispy/scene/canvas.py
	vispy/scene/entity.py
	vispy/scene/events.py
	vispy/scene/viewbox.py
	vispy/scene/visuals/line.py
	vispy/scene/visuals/visual.py
flakify
docstrings
Removed print statements
Moved some widgert code from old scenegraph to new
Removed old scenegraph
Reorganization
- moved Widget, SubScene, cameras, and systems out of viewbox.py
- moved viewbox to widgets/
Renamed examples/scenegraph to examples/scene
Entity.__repr__ hides name if it has not been set
Fix Line.__init__ args
Fix Visual.__init__ args
Merge remote-tracking branch 'vispy/scenegraph' into mouse_interaction

Conflicts:
	vispy/scene/visuals/line.py
flakify
Merge branch 'mouse_interaction' into scenegraph_reorganization
py3 fix
py3 style corrections