Explore link matchers being assigned to rows, not globally

[Tyriar]

In order to register/deregister link matchers and still have them active on the old rows they need to be assigned to the rows. There will probably also need to be some scope system; http link matcher is global (no row ref required), ls output link matcher is scoped only to the ls output rows.

More context: #538 (comment)

[Tyriar]

Link matchers are about to go, this sort of thing can be accomplished with link providers as you can classify chunks of the buffer using markers.