Add calendar selector for lightning URL-generator.

To-check suppress encodeURIComponent in getCalendarsForUser.
Yes, but indeed only in _getCalendarsForUser_, in this file, and without alarms, it looks trivial :  there isn't duplicates to prune anymore, juste one request to launch : 
```
Event.tags (err, tags) =>
    calendars = tags.calendar
```
do the same job.