  - Remote database on server is not locked dyring sync. operation. 
    We have to investigate this feature and use it if possible.
    See RFC4791 8.3. Use of Locking.

  - Improve unit test coverage. 
    Each state should be cover by tests

  - Created notebooks do not have their color set.

  - Settings thing is broken in multiple ways: NB#194278. First off,
    what is defined in the UI spec doesn't match the real
    implementation in "caldav.service". Changes will be needed to the
    UI spec. (FIXME: more details)
  
   - Some classe must be simplified and functionality should be 
     moved from one class to another
