Synchronize time range settings for Map and Dashboard views...and ensure they are valid

[erickj4]

Currently the time range sliders for the Map and Dashboard views are set to different defaults (e.g. at launch).

At the time of this testing, the default range on the Map slider is 06:00-08:00, but the range on the Dashboard slider is 2p-4p.

• These time ranges need to be the same: toggling between the views, we should see the settings on one reflected on the other.
• They also need to be valid: a time range that isn't possible shouldn't be shown (this is only a problem when the selected day is "today")

[erickj4]

NOTE: I just fixed the default issue --- starting up with the same, valid time range for both --- but NOT the sync issue!

[erickj4]

NOTE: I just fixed the synchronization issue, but the formatting of the time range slider on the Dashboard is not right..