Add system tests to create help screenshots and Wiki help text automatically

This PR provides a new set of Webdriver tests to create help screenshots and formatted Wiki text for the wiki help files. Importantly, it will create these screenshot and text files in whatever language is installed in the Joomla instance. So it can automatically create these files in any supported language.

See http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33436&start=0 for more information on testing.