Documentation enhancement for DataTable's column formatting and allowHTML

[jshirley]

[lsmith]

Thanks. I'll incorporate some of these, but there are a couple places where the object config obscures the option to use a key string instead. Also, all values are html escaped unless allowHTML: true is set, not just the output from formatters.

I'll clean up that paragraph.

[lsmith]

Merged with master and live-docs, then edited some text and entirely refactored that formatting example. It will appear on yuilibrary.com in our next site push. If you can branch from yui/yui3 live-docs for documentation updates in the future, that would be splendid.