Simple changes to load the new stylesheets and
implement some basic changes that make them work.

To enable in your respec document, set

    useExperimentalStyles: true,

in your Respec Configuration area.

In response to issue #520.

I had mistakenly had it default to 'div'.

Noticed that PR #499 changed the role to navigation.  This
PR changes the wrapper for TOCs to nav when using the new
experimental style sheets.  Added code to support both of these.
However, note that when using an nav element, the role of
navigation may be superfluous.  Opinion @stevefaulkner ?

This is to mirror changes in the experimental
stylesheet, and is only present with the useExperimentalStyles
configuration parameter is true.

If using useExperimentalStyles, then set the class
of def on idl containers so that new styles are brought in.

Better support for new styles in notes, examples, and webidl

Fixed some code style issues as per @marcoscaceres

WebIDL integration with styles is not yet ideal, but will give a decent
idea of what it might look like.