This is the first bit of code to move things over to jQuery. Datagrids, which previously required the now completely deprecated and nearly unavailable yui-ext, now works with jQuery instead.

jQuery is a popular, flexible, small and cross-platform JavaScript library. It's small enough where we can bundle jQuery with it (which I will do when I commit this), meaning that users of datagrids no longer have to install some third party library to use it.

I will be working on the rest of the Review Board codebase, moving things over to jQuery. For the time being, we can use jQuery for datagrids and yui/yui-ext for everything else, as they don't conflict.

Tested column reordering and customization on Firefox 3. Everything works fine. Before this is committed, I'll thoroughly test this on IE (perhaps building Selenium unit tests to test it).