Some lint tools warn about this, it's less work to just change it than
configure them specially.  There was previously some inconsistency with spaces
and tabs anyway.

Hiding this broke the indentation for nested lists.  This reverts to something
like the default Doxygen style.

This removes all the extra bundle content from the documentation output and
instead makes pages directly at the URI of specifications.  This way, links to
fragments in spec pages (which are often copy and pasted) are correct fragment
identifiers like <http://lv2plug.in/ns/lv2core#Plugin> instead of
<http://lv2plug.in/ns/lv2core/#Plugin>.