We currently only render pretty tables if they have the "top_table"
class set. All of our tables set this, except for the ACL & migration
doc tables, which should have set it, and the API reference which does
not want it.

Simplify life by rendering all tables in a pretty style and remove the
need for the "top_table" class entirely. A small rule turns off the
pretty style for the API reference where tables are a hack used to
render enums with horizontal alignment.
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>