pause on input side on the long queue

- MessageRouter will call input.setPause(sink.checkPause()) for every message before routing
- QueuedSink will checkPause() on the long queue, queue's half-full or queue size is over the threshold, by default 1 million
- LocalFileSink.SpaceChecker will pause input on its disk is being filled up

- BlockingQueue4Sink is deleted because it can potentially create a deadlock
Merge branch 'ISSUE-102'
fixed conflicts
conflict fixed