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.
support for reloading the billboard image