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