Sequencer: show option to open multiview/stereo 3d movies/images, and pre-load them
Sequencer: solve warning (misusing context)
Sequencer: proxy rebuild changes
Sequencer: final bits of seq->anim stripped away (in favour of seq->anims)

Sequencer core todos:
====================

* Check on proxies

* I may need a permanent flag to indicate something is multiview/stereo,
  to prevent overhead on rendering uncached. That should also prevent:

* Fix issue of mono-videos (when in multiview) not showing a valid view
  for all the views.

* Add multiview option to rna_sequencer_api add_movie_strip

* (optional) Remove duplicate code of creating anims for all views

* Test, Test, Test
Sequencer: remove unecessary 1-liner
Sequencer: small refactoring of the multiview image rendering code
Sequencer: unify the code to get the name of the files when using multiview + individual images
Sequencer: small style cleanup, and small code order change
Sequencer: Fix for monoview videos showing blank for missing views