Tests: Replace resource loader with AMD

:boom: WIP...

Pulll request's goal is to AMDify tests for 1.12.0 release and address part of http://bugs.jqueryui.com/ticket/10119.


This was supposed to be in the end of the `body`, not in the fixture `div` (needs fix). Anyway, the reason for moving it down was to favor rendering of other elements on the page before loading and executing these scripts.