Refactor settings and content wrappers to allow smooth overflows and properly show headers on mobile

Closes #4186, Closes #4190, Closes #4150

- Alters markup to allow for correct use of `-webkit-overflow-scrolling: touch;`
- Updates the debug page to use the same markup as the rest of the settings page
- Solve floating tag bar issue by making it absolute, not fixed
Merge pull request #4187 from PaulAdamDavis/settings-fixes

Refactor settings & content wrappers