Removing SimpleYUI 

This pull request is to complete the removal of SimpleYUI from the repo.

I have included the `build/` changes explicitly because this pull request represents not just src changes but removal of `src` and `build` files as well. I am aware that for most pull requests that one does not include the build file changes.

I have a few questions from the reviewers regarding changes I made:

1. Is it better to leave an empty array in `src/common/api/dist.json` and `src/common/api/yuidoc.json` so that the parameter is still there to be discoverable, or should that whole line be removed, including the config param?

2. I'm asking for feedback on these files' changes:
`src/loader/scripts/meta_check.js`
`src/loader/scripts/requires.js`
`src/yui/js/yui.js` 
because I am not as familiar with the inner-workings of these scripts and I want to make sure removing SimpleYUI is doing no harm.