Preliminary fixes and grooming.

* Tidy imports.
* Add module docstring and parser desription.
* Align arguments and keys.
* Fix missing default.
* Drop duplicate `-bmX` flags.
* Add commands to parser; drop `status` command.
* Fix bad combination of `with` and `try`.
* Do not parrot commands to output.
Group switches by type.
Derive key from argument automatically.