3D mesh painter
- refactor duplicate code from mesh-render/bake-render shaders
- keep from painting on one panel if other dirty
- remove floating gl* references, use inheritance instead
- optimization: create paint FBO only when needed
- show correct paint color for overlay brush
- fix "blurring" that happens to paint buffer on brush drags
- redirect key events to correct widget
- clean up texture/mesh ownership
- fix OpenGL context sharing across app
- swap Point2 typedef for QPointF
- add anti-aliasing to viewport
- bake around edges of UV view to improve texture filtering