Fix rebuilding of timeline dropdowns to show full reports timeframe

Timeline dropdowns should show the full span from earliest to latest report
regardless of interval (months/day). This fixes an issue where timeline
was limited to the same year as the active display.

Also fixes the selected dates to be the active display dates, not the
start and end of the timeline.
Fixes to the previous commit when we have no reports

Make sure we check we're actually getting dates for first/last report
if not use the active dates instead.
Tweak some whitespace
Fixes to date handling when we have no reports

Default to current date when there is no first/last report date
to get
Merge remote-tracking branch 'origin/master'

Conflicts:
	hooks/timespan.php
Revert "modified the JS the force the map to reload " now fixed in core

This reverts commit 4e780654f0502d7ad59f9018eaf3f07367871d39.