Timeliner: Design options for stop/loop on bubble end

[bkeese]

Description

For release of Avalon 6.5, these timeline options were removed (language comes from the dialog in the application):
Stop Playing at the end of the section.
Loop playback at the end of the section.
They stopped functioning when the change was made that de-selected all bubbles when media is playing.

Done looks like:

• Decide how to re-implement these features if we still want to stick to the usability problem that was solved by deselecting all bubbles when media is playing
• take into consideration the confusion caused by having bubbles selected that the playhead is not within.