Blender Git Loki

Various fixes for camera tracking stuff

- Fixed tooltip displaying for track sequence forwards in clip editor
- Corrected detection of 8 tracks so it wouldn't count tracks disabled
on keyframes.
- Scale track preview to actual track widget size instead of scaling the
whole preview image with given zoom ratio, so no extra memory needed to
store zoomed margin would be used.
- Track's statistics text will fit pattern position instead of search if
marker is disabled on current frame.
- Fixed toggle selection operator if selected track is hidden due to
"Hide Disabled" policy.