1. Refines the semantics of ghost creation, so that they only appear when
warranted.
2. Implements a mechanism for filtering out files which should not appear in comparison
results or be pushed along by updates.
git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@4525 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261
