lkairies-libxtreemfs_daemon_threads-review/contrib,server: Added option in libxtreemfs client and volume to start threads as daemons and extended the XtreemFSHadoopClient to use clients and volumes with daemon threads
lkairies-libxtreemfs_daemon_threads-review/contrib, foundation: Fixed IndexOutOfBoundException in XtreemFSHadoopClient and added missing constructor to RPCNIOSocketClient.
lkairies-user_guide_hadoop_integration_description/doc: Changed description of read-/write buffer and client-/group ID.
lkairies-user_guide_hadoop_integration_description/doc: Corrected typo in Hadoop description.
Merge branch 'lkairies-user_guide_hadoop_integration_description'
Merge branch 'origin/lkairies-libxtreemfs_daemon_threads-review'
servers: TestEnvironment: In case of errors during start(), shutdown all servers which were already started.

If the error was "Address already in use", also dump the remaining threads after the shutdown.
servers: TestEnvironment: Fixed NullPointerException when a start() failed and shutdown() tries to stop OSDs which were not started.