Create date poll: Add button and dialog to add hour range.

Clicking that button opens a dialog that allows adding a range of times
of day (hours and minutes) to a day. You pick:
* start time (of the time range),
* end time (of the time range),
* length (of the appointment), and
* period (for the time suggestions),
and the code computes the list of suggested times for you.
1 job for range-of-hours in 9 seconds (queued for 4 seconds)