3.3
* Make jubilee dates configurable, leave empty to deactivate
* Deactivate certain event types by setting an empty custom label
* New strategy for background syncs: identify changes and apply only these
* Reduce background syncs to every 5 days
- Optimize contact retrieval function                            
- Allow for multiple dates of same type per contact
- Set persistent id to calendar entries
- Reduce needed Android app permissions
