Create alembic version table in public schema

For some reason it ends up in the indico schema in production
Disable invalid end dates in period widget

 - set the minDate in the end date calendar correctly for repetitive bookings
 - clean up in the checkFrequency() function
Update moment.js 2.0.0 -> 2.8.3; add rrule.js

 - updated moment.js to the latest version (2.8.3)
 - added rrule.js (js implementation of Python's dateutil.rrule)
Disable invalid dates, fix repetition check

 - Disable invalid end date for repetitve booking according to the
   frequency.
 - Fix the repetition check, using rrule.js on the client side to
   match the backend.
 - Fix the computation of the nth days of the week of the month
   (ie. 3rd Friday of November) on the backend.
Post fix changes (code style)