[streaming] CoFlatMap & CoGroupReduce functionality
[streaming] Added database-backed state
[streaming] Memcached, MySQl and SQLite support for state management.
[streaming] Refactored db state connectors and added their license

Conflicts:
	flink-addons/flink-streaming/flink-streaming-connectors/pom.xml
[streaming] Refactored stream components with InputHandler & OutputHandler
[streaming] Minor bug and license header fixes