Fix field metadatacorruption on copy of lucene index

git-svn-id: https://svn.apache.org/repos/asf/maven/indexer/branches/lucene-4.6@1575155 13f79535-47bb-0310-9956-ffa450edef68
Make sure the nexus analyzer uses the correct tokenizer depending on the field. (Lucene caches/reuses the tokenizer, see https://issues.apache.org/jira/browse/LUCENE-3396 )

git-svn-id: https://svn.apache.org/repos/asf/maven/indexer/branches/lucene-4.6@1575156 13f79535-47bb-0310-9956-ffa450edef68