Split otioview into a separate repo

[jminor]

As we transition from otioview to the newer C++ based viewer, Raven, we would like to split otioview into a separate GitHub repository. This will allow otioview to exist independently from the core of OTIO.

That new repo can be created anywhere, then we can move it into the OTIO GitHub org: https://github.com/OpenTimelineIO/

[apetrynet]

Hi!
I'd like to work on this as a contribution to DevDays