Adds a community_name field to the employee datastream, which is then used to store the names of the communities that an employee is attached to.  This is written to on save in the employee object, which ensures that it and the RELS_EXT data it relies on don't diverge.
Update the catalog controller to be aware of the new community name field, pass it as the sole faceting option for Faculty special queries.
Merge pull request #355 from nu-lts/feature/solrize_employee_community_relationship

Feature/solrize employee community relationship