install the relation fetch job header
Manual revert of 7859c10a7511b96a67e7466c69a3c6a3ad575988.

Resource don't fetch the GID by default, resulting in GID always getting cleared
when the resource replayed the change and sets the RID. The change was
introduced for the google resource.
Starting CollectionFetchJob should not fail with invalid collections

If running CollectionFetchJob with a list of collections, where
invalid collection ids. CollectionFetchJob should run all subjobs to
return a list of valid collections.

KOLAB: 3829

Patch by Sandro Knauss
Revert "ItemModifyJob: support an empty set of tags."

This reverts commit c9b49056dd276762d924545dcb2a85ef96eb19a1.
ItemModifyJob: Deal with empty tag sets.

Required to clear tags.
TagSync: handle gid item references.
CollectionSync: Prevent double result emission