Adds a simple method for checking with Solr if this collection object has any children files or collections.
Remove red herring empty? method in nu_collection; turns out we're using SolrDocuments when we pull up smart collections.  Add is_empty_collection? method to solr_document_behavior to same effect.  Add checks to ensure that we only sure smart collections that have things in them to users looking at employee pages for others.
Merge pull request #450 from NEU-Libraries/hide_empty_smart_collections

Hide empty smart collections