Enable setting "config.hidepassed" from URL params

Loading a QUnit test suite with `?hidepassed` appended to the URL is useful for CI services that take a screenshot of the completed test suite upon completion in various browsers, for example.

Fixes #457

/cc @jzaefferer
Sorry, what specificially "shouldn't be removed"? The label text and description for hidepassed toolbar item is now contained in `urlConfig` side by side with `noglobals` and `notrycatch`. This is why I was able to delete all this code that unnecessarily special-cases hidepassed.