ymatsuda

Refactored Processor layer to add the ProcessorFactory.

1. Keep track of current StampedRecord and ProcessorNode in StreamTask.
2. Create ProcessorContextImpl inside StreamTask, and pass-in with initialization.
3. Remove KafkaProcessor and Punctuator, just use Processor instead.
4. Remove recordCollector in ProcessorContext.
5. Fix the timestamp tracking logic so that it is now monotonically increasing, ymatsuda could you double check on this logic also?

The interfacing classes with KStream would be in TopologyBuilder (addProcessor etc), and ProcessorTopology (getSources, getTopic etc).