Blender Git Loki

Manipulator: 3D view navigation improvements

- Highlight's were too intense/distracting
use more subtle alpha (consistent with the rest of our UI).
- Don't fill center cube (only draw edges).
- Draw widget while interacting since this is helpful in some cases.

Thanks to @jbakker for suggestions.

Also change axis hotspots so the nearest is always selected
for quicker axis picking (relies on dragging any axis to orbit).