Untangle wikibase.store module definitions

No module besides wikibase.store.FetchedContent should depend on
wikibase.store itself, since it does not provide anything.

Also make jquery.valueview.experts.wikibase.entityidvalue depend on
wikibase.store.FetchedContent.

Change-Id: I71e37799618dfcbee35b11f46099b8184fc21b6d