restore 1.6 compat

git-svn-id: https://svn.apache.org/repos/asf/maven/indexer/branches/lucene-4.6@1575162 13f79535-47bb-0310-9956-ffa450edef68
change version to 6.0.0-SNAPSHOT

git-svn-id: https://svn.apache.org/repos/asf/maven/indexer/branches/lucene-4.6@1575163 13f79535-47bb-0310-9956-ffa450edef68