Make the jsproj file more easily adaptable to newer YUI versions

I'm not sure if there was a good reason that each YUI file was individually added in the jsproj file, but it makes it extremely difficult to update YUIMetroTester to new versions of YUI.

This commit removes all of the individual `Content Includes` tags, and makes it so that all of the files in `src` and `build` will be automatically added.  It'll also make update PRs like #1 redundant.

Tested this out with YUI latest, and it works.