Add YAML-based lint rules

[Jeehut]

Problem Statement

Currently the only possible way to setup simple Regex-based lint rules is to write Swift code. While this allows a maximum of flexibility, it has drawbacks:

1. It's harder to write, understand or adjust rules for people who are not Swift developers
2. It relies entirely on Swift scripting which is not properly supported yet (see here and there)

Suggested Solution

Add a YAML-based rule configuration option where of course only the checkFileContents and checkFilePaths kind of checks are supported. It should be extensible though to include other YAML or even Swift configuration files where AnyLint would automatically include everything the right way to check all that's needed.