CameraTransition: Add support for rotation transition

[gkjohnson]

Fix #831

TODO

• Remove the need for a separate "targetPos" variable
• Make it simpler to extract the ortho position with height
• Add option for example to transition to predetermined viewpoint
  • shift perspective camera down slightly
  • consider just rotating the ortho camera orientation so it's facing the same direction
• Test and fix mid-transition toggle logic (right now it jumps)
• Add option for the transition camera transform can be applied when interrupting the transition