DONOTMERGE - data compatibillity braker

Brake compatibility with actual calendar's data.

* changed date convention in database: data and API is in UTC, the client has the Cozy's timezone
* client's dates are now handled with moment-timezone
* upgraded to fullcalendar 2.1.1
* improved recurring events
* added all-day events support (fixes #102)
* added event's reminder support (partly fixes #97)

This will probably fix or help to fix #105, #108, #117.