#20 Calendar and timesheets arhiving interface

[Ivana]

The calendar and timesheets arhiving interface is not user friendly.

The least info it should contain:

* What archieving means: archived events no longer in ops client (sunbird) but still available for reporting
* user can only log their calendar
* admins can choose one of two: archive all timesheets or all calendars
* archive date is included

And preferably, archiving should be i18