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Small fixes and features:
- Fixed broken toolshelf for empty space clip.
- Added option to hide disabled tracks.
- Do not send disabled markers to tracking job.
- Fixed bug with disabling marker when tracking backwards.
- Fixed bug with unset principal point by default.
- Hide bundle projection for disabled markers.
- Flip orientation when hitting "Set Axis" when bundle is
already defines axis.
be73c3bd4c