Also fixed unit tests so they run but some still fail
- Added IUserSession mock
- Replaced OCP::getUser() with IUserSession usage to make the mock work
- Added base class for test cases
- Moved adding/removing groups to OCA\Contacts\VObject\VCard
- CATEGORIES property wasn't removed when empty
- When removing all groups from contact, it wasn't assigned to ungrouped.
- When adding contact(s) to group it wasn't removed from ungrouped until
you changed to other group and back.
