Blender Git Loki

Rotation support for motion tracking markers

Implemented general transformation tool Rotation for motion tracking data.
Mainly used to rotate pattern of markers.

To achieve most of usability, added configurable pivot point which is in fact
was median point before, but now can be chosen from boundbox center, median point
or individual centers. Individual centers means transformation would be performed
around marker's position, which is useful for rotation and scale.

Also implemented alternative scaling transformation -- hit S, S leads to
scaling of pattern area only.

TODO:
- clamping in some cases isn't working well, but that's easier to be resolved
after moving search are to marker.
- Update startup.blend so clip editor in Motion Tracking screen would be set to
Individual Centers by default.