[CYB-3, CDAP-493] js ingest library with complete integration tests

This branch was created to resolve in more safer way merge conflicts.
is it possible to specify start/end times in this request (similar to java integration tests), so that previous runs of the integration test do not interfere with the assertions in this run?

(otherwise if the streamWriter.write() fails for one test execution, this might still pass because the event was in the stream from before the test ran).