OAK-2229 - Provide a way for Index implementation to determine reindex modee

When reindex would be done IndexUpdate would increment 'reindexCount' in the index definition node. Index implementation can use that to determine the index generation/revision

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1634779 13f79535-47bb-0310-9956-ffa450edef68
OAK-1724 - Enable copying of Lucene index to local file system for read queries

Handle the reindex case. Make use of reindexCount introduced with OAK-2229

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1634781 13f79535-47bb-0310-9956-ffa450edef68