Update README to reflect bookkeeper modules

git-svn-id: https://svn.apache.org/repos/asf/zookeeper/bookkeeper/trunk@1631681 13f79535-47bb-0310-9956-ffa450edef68
Add JNA license in NOTICE files

git-svn-id: https://svn.apache.org/repos/asf/zookeeper/bookkeeper/trunk@1631683 13f79535-47bb-0310-9956-ffa450edef68