DONOTMERGE - Guillaume works

Brake compatibilities with actual cozy-calendar and actual cozy-sync, to achieve these :
* 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
* added all-day events support
* added event's reminder support


( Stand for on september the 18, 2014 : addTimezone is not used ) I don't know well what to do with VTIMEZONE in iCal. I think nobody truelyy use it, and rely more likely on library like moment-timezone. But, experience may contradict me.