Blueprint-defined "bookmarks" for view + timeline control

[jleibs]

When working with a dataset it is often the case that the author generating the dataset knows about specific events and time-ranges that are of particular interest.

Although the blueprint now allows us to specify a specific timerange for the blueprint, we can only do so once globally. It would be nice if the user could provide several "named" time range configurations with a UI interface to single-click and jump between them.

[PeterMitrano]

Just adding some questions/thoughts here on how this might work:

• you want one for time events and one for sequence events
• you may end up with two overlapping bookmarks if generating them via code so how would that be displayed?
• bookmarks could perhaps be tied to an entity path such that they get hidden or shown based on the entity path being hidden or shown
• Adobe premiere may be a good implementation to reference