SOLR-5226: add lucene index heap usage to the solr admin UI

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1530169 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5251: add DocumentDictionary

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1530229 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5314: Shard split action should use soft commits instead of hard commits to make sub shard data visible

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1530267 13f79535-47bb-0310-9956-ffa450edef68
WIP