Pages in views (2)

More work on #7627

@ewinslow This rebases, rewrites commits, reverts the segments passing, and reverts conversion of the admin and cron pages (I think exposing these to plugins is a bad idea without a very good justification). If this looks good you can reset your branch to this one so we can keep working on the original PR.
I feel like all these breadcrumbs should get moved to the views as well.