Integrate PhantomJS support via GhostDriver

[beercanx]

Most of the work has already been done in substeps-ghostdriver although depending what happens in Improve configuration of Substeps more work to allow the same level of configuration maybe required.

[davemoss]

IIRC, ghostdriver isn't required any more. PhantomJS talks native wedriver protocol. Just create a RemoteWebDriver pointing at the PhantomJS instance.

[beercanx]

PhantomJS I didn't think it talked native webdriver, it does come with GhostDriver bundled in to handle all the Remote Webdriver communications.

What the old GhostDriver project also provided a PhantomJS Driver, which handled the starting of PhantomJS locally so there was no dependency on manually starting a server some where else to handle the remote webdriver requests.