Animations timeline contents not saved in session

[Elaine Meng]

Without the ability for people to save their timeline work, and ability to correctly restore window size when Animations was open at time of session saving (separate ticket #19891), the tool is nearly useless. Typically for working on any complicated presentations and being able to reproduce them later, people will need to save/restore the session several times.

Restoring status into sessions (actions, scenes, transition types, etc.) is required for this to be useful enough for production release.

(Also important but not quite as crucial is that there needs to be more work on scenes/transitions for full realization of Animations tool capabilities.)