First cut at new rotation UI/UX

Basic support for 3 new "grab handles" for rotation of entities.
* renders handles for yaw, pitch, roll
* moves handles to correct corners of entity as you move around the entity
* clicking on the handles will show the two circle UI/UX for rotation
* dragging around inner circle snaps to 22.5 deg rotations/outer circle is free rotate

Some problems that still exist:
* display of hash marks is not 100% correct because the hash marks move with the current rotation
* display of selection/stretch handles gets misplaced after entity has been rotated **NOTE: I'll fix this ASAP!**

Some additional features:
* Properties dialog box now works properly in the new tool. It wasn't wired up before.
helpful new helper function for calculating angle between two vectors... used in the rotation JS code