[PROJECT] OTIO Improvements

[ThomasWilshaw]

Once #1562 is merged Olive will have very basic but usable OTIO support (at least for importing). This is a todo list of things we need to improve our OTIO support.

• [x] Finish and merge #1330
• [ ] Refactor/cleanup OTIO load code as it's quite messy and hard to maintain #1823
• [ ] Handle footage with no media reference
• [ ] Create some kind of default "Footage missing" type onscreen display for playback
• [ ] Test with OTIO examples and Netflix Open Content
• [ ] Test OTIO saving code
• [ ] Add support for image sequences (OTIO docs)
• [ ] ...

At the moment there is no correct way to test if an OTIO file has been properly imported/exported other than by eye so really what we need is real world usage. If anyone has any projects edited not in Olive that they could create an OTIO file for and then comapre Olive's result to the original that would be very helpful.