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


A real question behind this : VComponents (and subclasses) can be instantiated with arguments, typically in toICal methods, but althought in the iCal parser, but without any arguments. This line (and its friends in others sublcasses) is a dirty _quit quick_. Is there a better solution ?