Fix warning about moment().add()

The order of the parameters changed on recent releases, so moment was
showing a warning
Fix date selector on top

Was broken because datepicker now doesn't work on a hidden field.
Fix cell clicking/selecting to create new events
Fix select helper on agenda views

Now using the select helper shipped with Fullcalendar
Fix error when dealing with events with no reminders

Check in first place if the event has any reminders configured
Fix event resizing and dropping

Fullcalendar seems to have a bug with all day events, so this part
needs some work