Share test params between tests inside a scenario

Sample:
https://github.com/wangjungithub/arrow/blob/share_testParams/tests/functional/data/arrow_test/test_params_share.json

webservice controller is added at tests/functional/data/arrow_test/share_test_params/webservice-controller.js, you can move it to lib/controller to be a Arrow built-in controller if it is good enough :-)

Documentation is also updated.

Thanks,
Jun (junwang@)