Select rules by name

[LiamPattinson]

Adds a basic implementation for #106, so you can now specify the full names of rules:

fortitude check --select=implicit-typing

Also works in settings files.

Missing some features:

• Can't specify categories by full name, so --select=typing doesn't work.
• Human-readable names are mapped 1-to-1 with rule codes. In the future we'll likely need multiple human-readable names and multiple codes mapping to each rule.

Ultimately I think we'll need to add more macro machinery to do it properly, but right now I'm still having issues figuring out how everything fits together.

[ZedThree]

Amazing! 🎉