This commit includes the major changes between DAVdroid and EteSync. It
adjusts the app to use the EteSync protocol and server. It includes some
ugliness still, and it's a squash of many ugly snapshot commits while
hacking on the initial DAVdroid code.
History should be "clean" from this point onwards.
* change group methods to less specific values
* new account settings version: change group method to CATEGORIES for updated accounts
* change group method from CATEGORIES to GROUP_VCARDS automatically when a group VCard is received
GUI:
* AccountSettings: disable CalDAV/CardDAV options when the corresponding service is not available
* AccountSettings: new option to choose contact group method
* account setup: allow to choose contact group method at account creation
* rewritten contact group support to support VCard3 CATEGORIES and VCard4-style KIND/MEMBER groups
* new account setting: contact group method (VCard3/VCard4/Apple "VCard4-as-VCard3")
* keep unknown properties when saving/generating VCards
Tom Hacohen