Revamp IIncrementalIngester API again for clarity and efficiency

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/branches/CONNECTORS-1118@1644386 13f79535-47bb-0310-9956-ffa450edef68
Convert deletion methods to also cut back on loading of instances

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/branches/CONNECTORS-1118@1644390 13f79535-47bb-0310-9956-ffa450edef68
Remove unused reference

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/branches/CONNECTORS-1118@1644391 13f79535-47bb-0310-9956-ffa450edef68
Refactor IIncrementalIngester API further for efficiency and clarity.

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/trunk@1644399 13f79535-47bb-0310-9956-ffa450edef68