event: Do not send event start and end time multiple times

closes #4
form: datetime no longer breaks

An issue was previously identified which would cause datetime to break
when the browser refused to parse the default value (the case where the
browser had implemented the datetime-local html5 field).  To ensure a
constant experience across browseers, I just went ahead and overrode it
completely and we now use a class to designate what the field type
should be

closes #3
form: add a multidate field

The muiltdate field uses Dynarch Calendar to enable users to choose
multiple dates.  This is immediately being used on the event_add screen
to allow an event to be added for multiple dates at once.

closes #1