Requests for comment/Redesign user preferences

This is a requests for comment regarding redesigning user preferences.

Background
Special:Preferences is currently pretty ugly. It should be redesigned (cf. 62559).

Implementation
62559 is the tracking bug. It has a number of easy subtasks (tree).

Mock
This is a very rough mock-up related to 63583. Each section will be collapsed using JavaScript. The top section ("User profile") will be auto-expanded by default.