Provide a mechanism to communicate a mime type (if known) from repository connector to output connector, and hook this up into the Solr, Web, and RSS connectors.  Part of CONNECTORS-613.

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/trunk@1434653 13f79535-47bb-0310-9956-ffa450edef68