Moving to YAML allows the configuration data to be read by C programs.
Also go back to using YAML::XS since it is the only implementation that has proper boolean support.
YAML::XS requires libyaml so it not as portable as pure Perl versions of YAML.
Instead of using YAML:PP just use the general YAML::Any module which uses whatever is installed. We are not concerned about performance for YAML so whatever works is fine.
