Standardize classnames and layout to facilitate theming

Working notes on standardization of classnames and layout across Moodle activity types, with the intention of making theme design faster and more foolproof.

In order to be sure all bases are covered in standardization, it's probably good to begin with a Survey of existing page views and markup. I'm going to exclude editing screens from this survey because it would just be too much to cover.

Once we've got that survey complete, we can begin to make recommendations for standardization which will work for as many of the surveyed page views as possible.