Calendar event functional test

Mainly, I implement functional test cases for the SpringCRM calendar.
Along the way I fix some issues:

- Move business logic from the CalendarEventController to a new
  CalendarEventService class.
- Implement a way to remember the currently used calendar view and
  restore it after saving or deleting.
- Make events in day, week, and month calendar view editable which
  allows moving or resizing events in order to change start and/or end
  time stamp.
- Add button to go to a particular date.
- Add additional validators to calendar events, recurring events, and
  reminders.
- Add create button to show view.
- Display missing reminders in show view.
- Let Reminder implement MessageSourceResolvable in order to use it as
  message source in show and list view.
- Fix a bug in the JavaScript function String.parseDate(): a variable
  was not defined.
- Fix tab/space mismatches and make code "more groovy".

Furthermore, I remove the "Home" link in the main navigation in order
to allow opening the subnavigation on tablet computers where no mouse
over is available.  Also, I increase the z-index of the main navigation
because it was partially overlapped by some calendar views.