Scheduler changes to support CONNECTORS-781.  Introduce a new database table to track bins, and implement minimumDepth using lock manager constructs to work cross-cluster.  WARNING!!! Schema change!

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/trunk@1546965 13f79535-47bb-0310-9956-ffa450edef68
Creating rebased CONNECTORS-781 branch

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/branches/CONNECTORS-781@1546968 13f79535-47bb-0310-9956-ffa450edef68