Add build dependency to backgroundAdminServer task

- For jsTest task, invoke 'classes' task to build the spring-xd-dirt
  resources before starting backgroundAdminServer
XD-910 Add a processor for client http requests

--Refactored the module to handle a payload.
XD-906 Add aggregate counter monthly resolution

* Create an enum for the package and use this in preference to Joda DateTimeField. We don't need any of the latter's functionality anymore and it can't be used for months or years.
* Add query by month to aggregate counter.
  - Also changed the test to run across more date boundaries (e.g. 2013-2014) and fixed some bugs related to this.
* Add new aggregate options to shell
* Fix potential NPE in aggregate counter
  - When querying beyond with day or month resolution beyond the interval where data is actually recorded, a null value could be returned from the bucket store and cause a NPE. This is now checked and an array of zeroes is used instead.

Jira: https://jira.springsource.org/browse/XD-906
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
Remove serialization warning
XD-924: Split .x package into 3 additional projects
Relax dependency on twitter stuff
Move projects into an extensions/ directory