XD-578 Can't access HDFS using the webhdfs protocol

Also address XD-901 regarding different dependencies for webhdfs
in different Hadoop distributions.
Fix SingleNodeMainIntegrationTests' server stop

- Invoke stop() on SingleNodeServer in @After test method
  rather than inside the test method itself
  (This guarantees the server is stopped after each test
   irrespective of test result)
Extract CORS support in dedicated class
XD-915: Convert tcp modules

Converts tcp modules to new form (separate project for source and sink).

Adds tests for tcp modules.
Suppress warnings for CompositeCodec in tests
Revert OptionsRequestCtrl as it conflicts with static pages
XD-915b: Apply to mqtt Modules

Update mqtt version to SNAPSHOT