rotation gizmo usability problem/suggestion

[mustcode]

Not a critical bug, but this will allow the LOCATE_VIEW and LOCATE_WORLD mode for rotation gizmo a lot more useful.
currently, rotation gizmo doesn't always rotate the object around the gizmo's "visual-axis"... meaning, the X-Y-Z arc rotate the object along the object's X-Y-Z axis, and after a few rotations, user will not be able to tell how the rotation axis is oriented (unless the gizmo is set to LOCAL mode). Ideally, regardless of whether the gizmo is in LOCAL, WORLD, or VIEW mode, the object should always rotate according to the visual arc visualized by the gizmo.

Thanks for a great lib, I found it very useful and I'm sure others will too. Keep up the great work!