Parse rules and actions yaml headers like we do with content headers

[Arnaz87]

This is how it's currently done (and for actions), the problem is that it breaks if the header is not exactly how the package manager expects it, even if it's valid yaml.

This is how it should be done (gotten here), it works for any yaml header as long as it's separated with ... from the body.

[naturallymitchell]

parse it and change existing files' syntax to have the three dots above and three dashes below, or something