Blender Git Loki

Tweaks to plane track

- Do plane re-evaluation only when transform is actually done.
Before this re-evaluation happened on every mouse move.

- Added a flag "Auto Keyframe" for the plane track, which does:

* If Auto Keyframe is enabled, then every manual edit of the
plane will create a new keyframe at current frame and update
plane motion between current frame and previous/next keyframe.

This now also implies blending detected motion with neighbor
keyframes, so there's no jump happening.

No automatic update on manual point tracks edit will happen.

* If auto Keyframe is disabled, then no keyframes are adding
to the plane and every plane tweak will re-evaluate in on
the whole frame range.

In this case manual tweaks to point tracks and re-tracking
them implies plane re-evaluation.