Standardize config entity routes.

Core has standardized the entity route names to match their relationships.
This means that "$entity_type.edit" becomes "entity.$entity_type.edit_form", same for add and delete.
Change notice: https://www.drupal.org/node/2306387

This change did not include the list route, even though it is a needed change as well.
I've talked to Berdir, who confirmed that the current best practise is to use "entity.$entity_type.list", so I've implemented that. It makes the generated routes nice and consistent.

The same change needs to happen for the generated content entities, but doing it for config entities allows us to start small.