Schedule Agenda: add markers and a drag icon to make it easier to know how to position the time bar

[dasgarner]

It isn't obvious how to use the time bar - the best way to use it is to drag and drop, so we should make that more obvious. We could also help identify where in the bar you need to go with markers.

• [ ] Add markers to the time bar
• [ ] Change the cursor pointer to one which indicates its drag-gable