Blender Git Loki

Bug fix - own collection.

- Scopes in Sequencer were not drawing OK (drawing code assumed alpha)
- Histogram in Sequencer now uses same formula to quantify R G B as the
other histogram in Blender (per channel).

I seriously thought of dropping this, and add the same sidebar here as we
have for Image window. However, what stops me is that current code is
very optimized, and has OMP hints.

Will check instead on cleaner drawing here now.