add carddav-search option for X-ADDRESSBOOKSERVER-MEMBER

Adding field X-ADDRESSBOOKSERVER-MEMBER
which can be used to relate persons to groups (macos behaviour).

- groups are cards with field X-ADDRESSBOOKSERVER-KIND == 'group'
- and all members' UUID/URI in the X-ADDRESSBOOKSERVER-MEMBER array of that group-card.

Signed-off-by: labor4 <schreibtisch@labor4.ch>