Document organization for the release v0.4.0.1 branch (#1981)

To-do:
1. Properly move Crate improvements into the correct categories
- [x] Split this paragraph into two paragraphs: global flags and
VehicleType flag
  - [x] Add a global flags category and organize the content
- we currently have many features that are only global flags scattered
in various places
- [x] Convert the global switches that are off by default in `##
Bugfixes and miscellaneous` into a feature paragraph.

Author: DeathFishAtEase