Release 6.22.0: Timeout parameter to wait for combined CardDAV requests

[changerequest]

The Mac Addressbook CardDAV client sometimes sends concurrent requests that logically belong together, e.g. a contact creation followed by a contact group assignment - here, the server can't update the group until the contact has been successfully created due to the other request.

This parameter specifies the maximum time in milliseconds how long the server waits for other, needed requests.

The file 'contact.properties' is therefore enhanced by property named com.openexchange.carddav.combinedRequestTimeout with its default set to 20000.