Revisiting the revision tab on entity pages

@stevector I haven't thought too much about the details here, just that we need more granularity than one single permission for all entity types :) So I'd be happy for input here. But a good start is probably to have permissions per entity type and per bundle (for those entity types that have bundles).

Semi-related thoughts

I think the revisions tab/page for entities probably need some thinking through in general. I threw together multiversion_ui.module more or less for the wow-effect in LA, without much thought into what we actually need on this page. A visual revision tree with colors highlighting conflicts was just cool I thought :D

So taking a step back, how do we build this revisions page such that it integrates well with modules like Workbench Moderation etc? Should Multiversion even be responsible for providing the UI at all?

I'd definitely need some input on this topic. I want to make sure that everything plays well together :)

The first iteration of this should just fix these two methods:

• \Drupal\multiversion_ui\Controller\RevisionController::viewTitle()
• \Drupal\multiversion_ui\Controller\RevisionController::view()

We should be able to get inspiration from these methods:

• \Drupal\node\Controller\NodeController::revisionPageTitle()
• \Drupal\node\Controller\NodeController::revisionShow()