Update and cleanup settings for Wikidata

* add settings to allow things to work until pending schema changes happen
* disable data transclusion for wikivoyage clients
* add wikivoyage to wikibase siteGroups
* add shared cache key settings
* explicitly require WikibaseDataModel
* re-add WikibaseDataModel to extensions-list (should be fine now, since
is used on all current deployment branches)
* removed settings that are now same as defaults in Wikibase
* other cleanup

Change-Id: I61d9a9d5146af5b94f94820113ef69d38826e93f