Add --quiet switch to runserver

It hides successful requests to common static files
Wrap cformat-ed strings to get the correct len() etc.
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)
Fix invalid bysetpos type from float to int

Fix failing tests