CDAP-471

1) In standalone, now stops all components, if one fails. JIRA issue has been opened to restart runnables if they fail: https://issues.cask.co/browse/CDAP-477
2) Validate the handlers that user passes in during deploy time
3) Move construction of NettyHttpServer to constructor of ServiceHttpServer (from startup)
4) Add a small test case to test (2)
Isn't the comment at the top of verifyHandlers() method sufficient? What more do you mean?