Shorter authoring format

[darobin]

We could produce a simple library, in the spirit of ReSpec that allows authors to write using a really simple HTML variant and that takes care of producing all the more complicated markup, notably the metadata. It's a fair bit easier than for standards, so not that much work.

We could even support embedded MD, like ReSpec, but handle it more cleanly by using <script type=md> sections (so that embedded markup works more easily too).