Refactores navigation (drawer) fragment
Adds synchronize service and startup fragment

Synchronize service is responsible to send sync-request  to the android
framework but also collect information about syncs (like when the last
sync happened).

The corresponding fragment will use the new sync service to determine on
app startup whether a first/initial sync is necessary or not.
Adds star publisher activity
Removes accidentally committed temp files
Adds "no content" view (image and description) to event fragments