OAK-1994 - Oak Console improvements

-- Limit the no of child dump to 50 by default. Use 'ls <no of child>' to change the limit
-- Fixed issue in cd command to cd to absolute path

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1613354 13f79535-47bb-0310-9956-ffa450edef68