Blender Git Loki

Camera tracking: operator to setup scene for compositing things into footage

This operator does needed changes to

- 3D viewport
- Scene settings
- World settings
- Compositor
- Scene objects

in a way scene becomes ready to be composited into footage.

Known issue: preview doesn't work "out-of-box" after running this script,
selecting View node and hitting Tab helps. Not sure it can be solved
in nicer way at this moment.