Unified config and added YAML (syntax) support (#113)

- Unified config to stratosphere-conf.yaml, which replaces the old
  nephele-user.xml and pact-user.xml and is also read by
  bin/nephele-config.sh

- Removed some settings from config:
    * instance configuration
    * multicast for broadcast
    * profiler impl classes
    * jobclient.polling.interval (adjusted default from 5 to 2)
    * pact.runtime.fs_timeout