In recent changes the viewport_quality setting was not working what
users expected. This change will separate the anti-aliasing method that
is being used.
We now have three settings:
- scene.display.render_aa: Will be used during Render Image.
- scene.display.viewport_aa: Will be used during Viewport Render Image.
- userpref.viewport_aa: Will be used in the 3d view.
The viewport_quality setting has been replaced by the viewport_aa
setting as it was the only thing in currently controlled.