Presently we indicate that table elements can allow for any role, and while this makes sense in the context of the legacy issues of table misuse it's not really accurate for modern web development.

Additionally, there needs to be more clarity specifically for table descendants that "any role" is really only applicable if the immediate table ancestor is not exposed as a table or grid. For instance, the following is nonsense but presently throws no validation errors.

<table>
  <tbody role=article>...</tbody>
</table>

This issue closes #97