The local admin of a subwiki should not be allowed to alter the index of entities outside that subwiki

The Solr index script service should always verify that the wiki of each of the entities that are about to be indexed by a user is a wiki where that user has admin rights, otherwise fail the operation.

This also needs to be reflected in the Solr Search Admin UI by always showing one (current) wiki when viewed from a subwiki and all the wikis when viewed from the main wiki.