Implemented new VOEvent parameters and allowed preliminary VOEvents to include skymaps (although they aren't required to).

a plot of recent events on the landing page. The latter is
only shown if settings.SHOW_RECENT_EVENTS_ON_HOME is True.
Setting it to false for now, since we are not in a run.

Also added Reed's tutorial on LVAlert.

Localize EMFootprint start times to UTC.
Changed event creation time query to assume UTC.