BOOKKEEPER-615: Twitter stats implementation of stats interface (sijie via ivank)

git-svn-id: https://svn.apache.org/repos/asf/zookeeper/bookkeeper/trunk@1536635 13f79535-47bb-0310-9956-ffa450edef68
BOOKKEEPER-698: Bookie client closure is not considering timeoutExecutor (rakesh via sijie)

git-svn-id: https://svn.apache.org/repos/asf/zookeeper/bookkeeper/trunk@1536965 13f79535-47bb-0310-9956-ffa450edef68
BOOKKEEPER-700: GarbageCollectorThread exsiting with ArrayIndexOutOfBoundsException (rakeshr via ivank)
Update to stats API to use enums instead of strings
BOOKKEEPER-699 Codahale metrics implementation of stats API
BOOKKEEPER-696 stats collection on bookkeeper client