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


This might be more readable 
```coffeescript
options.byweekday = [
    [
        RRule.SU
        RRule.MO
        RRule.TU
        RRule.WE
        RRule.TH
        RRule.FR
        RRule.SA
    ],
   [ moment(event.start).day() ]
]
```