Remove discoveryManager

(do not merge immediately -- not tested with yarn. (should not make any difference) )

Fix for issue: https://github.com/stratosphere/stratosphere/issues/18

I removed the DiscoveryManager, as it is not really used.

The detection of the TaskManager's own IP address does not need a RPC service at the JobManager. It is determined based on the network adapter that successfully connects to the JobManager.

Please review my implementation.