merging media overlays

I'm slowly coming around to the idea of merging media overlays with the rest
of the core, even if it is a bolt-on optional technology. The fact it was
assigned a core 3.X incrementing number does make it stick out if not
incorporated, but more usefully it just harmonizes things like the schema
and vocabulary definitions together, and doesn't require cross-referencing
all the terminology.

 

Here's what it looks like merged:
https://mattgarrish.github.io/publ-epub-revision/epub33x/spec/epub-core.html

 

The one oddity is that the reading system behaviours are much better spelled
out for media overlays than for the core specs, so we kind of go from almost
bullet form things a reading system is required to do to prose explanations.
But maybe that's part of what we need to fix in terms of testing, too.

 

Matt