Create snapshots UI

[sashaouellet]

A UI must be provided to the users to allow them to create "snapshots." Up front, we'd expect to want this for shots, but should be general enough to be repurposed for assets as well.

The idea is that users would create a snapshot of a shot by inputting a playblast, render, etc. and this would be stored as the latest snapshot of the particular shot. We can then aggregate all the latest versions and string them together for a dailies review.