Use breadcrumbs instead of titles

See #441 (comment 505565)

Are breadcrumbs something we want to have? If so, let's design here how we want them to behave

#714 (comment 603598) answered:

Also we should stop with h1 title I guess, in favor of a breadcrumb with a title embedded, but that's something that we can discuss in !1782 (merged) IMO.

Edited by Raphaël Hertzog