Pr maya nav

- User can switch to maya style navigation schema in editor setting. 
Alt + Left drag = Orbit
Alt + Middle drag = Pan
Alt + Right drag = Zoom
- Add non-uniform scale support for 3d spatial node.
- Fixed display message for transform mode switching

Notice:
Reusing TRANSFORM_VIEW as switch to uniform scale. Might be better to add TRANSFORM_UNIFORM enum value, but that's more lines of code :)