Follow doc-ock evolution.
Follow odoc evolution.
add word-joiners between the question mark and the identifier of optional
fix handling of stop comments
put id on nav
class types: fix rendering, they were previously rendered as classes.
place docstring above include not below
handle substitutions on first class modules
switch to jbuilder
use "display type" to render canonical modules as "module Foo : sig .. end"
instead of "module Foo = Foo" (which was confusing)