ACCUMULO-875 added API and shell command for listing active compactions on a tablet server

git-svn-id: https://svn.apache.org/repos/asf/accumulo/trunk@1435371 13f79535-47bb-0310-9956-ffa450edef68
ACCUMULO-956 applied patch from Brian Loss

git-svn-id: https://svn.apache.org/repos/asf/accumulo/trunk@1435383 13f79535-47bb-0310-9956-ffa450edef68
ACCUMULO-513 Added API and shell command for pinging tablet servers.  

git-svn-id: https://svn.apache.org/repos/asf/accumulo/trunk@1435416 13f79535-47bb-0310-9956-ffa450edef68