Revise to retain older default functionality

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/trunk@1571602 13f79535-47bb-0310-9956-ffa450edef68
Revise to retain original default content type determination

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/trunk@1571603 13f79535-47bb-0310-9956-ffa450edef68
Fix for CONNECTORS-901

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/trunk@1571614 13f79535-47bb-0310-9956-ffa450edef68