Convert tests to casper API (bug 1045707)

This converts us over to using the casper 1.1 api directly and removes the abstraction layer and updates everything to the current version of casper which is 1.1-beta3
While you are at it, it's not a new problem, but could you please add `LC_ALL=en-US` before calling casper ? A lot of tests depend on the locale, and casper's `navigator.language` is different depending on how the locales are set on your system.