Implementation of smoke tests using Ghost


* Added a flag -agent in suite.py to decide the agent to be used for smoke tests
* Added setAgent method in BrokenLinkTest class
* Moved ReportData class to a new file
* using_twill/using_ghost has two different implementations of login and visit methods which are imported as required.
Please see the updated documentation for more details

http://eden.sahanafoundation.org/wiki/DeveloperGuidelines/Testing/Smoke
http://eden.sahanafoundation.org/wiki/DeveloperGuidelines/Testing