The menu sets up divisions between "Core/Extension" (which are similar but
different -- two styles of packaging and collaboration) and "API/Hooks"
(which are similar but different -- two types of interfaces).

More hook fixes

extend-stages - clarifying intro paragraph

Hook fixes for L, M, N, and O

Conflicts:
	mkdocs.yml

This completes the migration of all hooks pages to close #71
and also sets the theme to Material

Conflicts:
	redirects/wiki-crmdoc.txt

real content