agenda+ New lreq doc format

See section 7 at 
https://w3c.github.io/sealreq/khmer/indexnew.html#h_lines_and_paragraphs

I'm following the style of the Language Enablement Index to point to 
links relevant to each section.  If there's no actual text for a 
section, these link lists will still be there.  The subsections in 
section 7 provide a nice assortment of eventualities.

This should enable us to simplify the LE Index, which would be good 
since we (I) regularly forget to maintain it, and it is also a little 
complicated to maintain at the moment.

I also added some asides at. the top of each section indicating what the 
section should address. (There are similar things in the gap analysis 
docs and the LE Index.)

what do you think?