Streamline "Roles & Permissions" screen

[frandavid100]

The "Roles & Permissions" screen can be made much easier to read, and also save space. Here's a mockup of how that could be done:

The idea is: each role is in a box showing its power level, users with that role, and permissions for that role. Users and permissions can be added to a role by typing their names in the box.

A "New role" button lets you create custom roles, and there's a dropdown that lets you edit their power level and their name (if naming them is even possible), as well as delete them.

[HarHarLinks]

I think this is a good idea to view users' roles, but I'm not sure about permissions for the simple reason that it is nontrivial to find the role that has a certain permission.

[SimonBrandner]

I am going to close this in favour of #22774 as the whole tab should probably be redesigned, so it makes sense to keep it in one issue