Youngsuk

Change summary:
- MessageBroker (js/messagebroker_ex.js) has been extended to support topics. It internally uses EventManager.
All topics subscribed at EventManager will be propagated to the MessageBroker.
- DOM related operations were factored out to DomHelper class (js/domehelper.js) including maintaining list of iframes, resizing, converting object nodes to iframe nodes.
- Unit tests for Event Manager and MessageBroker functional.

Known issue: multiple subscription from same iframe results in multiple subscriber of same handler (The correct behavior is to have only one subscriber per iframe regardless of multiple subscription)

PENDING:
- Modify the message format to the recently agreed with Inkling.
- Fix the above issue
- Add scanning feature to DomHelper and add DomHelper unit test.

Disregard widget-*.js files, they are files still in progress. 

Cheers.