Blender Git Loki

Camera tracking: improvements of track preview widget

- Enable bicybic filtering fir image displayed in track preview
- Option to show grayscale content of track preview
- When some channels are disabled, display exactly the same
content of preview image which is sending to tracker library.

Merged from tomato branch using command:
svn merge -r42382:42383 -r42384:42385 -r42394:42395
-r42397:42398 -r42398:42399 -r42406:42407
-r42410:42411 -r42417:42418 -r42471:42472
^/branches/soc-2011-tomato