Add support for YAML formatted config file

[jonbullock]

So more complex data structures can be used.

No specific use cases as yet, will be done once requirement exists.

Research:

http://www.yaml.org/
http://stackoverflow.com/questions/450399/which-java-yaml-library-should-i-use
https://code.google.com/p/snakeyaml/

[s17t]

Also consider TypeSafe conf library [0]. It doesn't support YAML but HOCON is kind to human being too and it also support plain JSON, properties files and more like Inheritance.

[0] https://github.com/typesafehub/config

[jonbullock]

Thanks, that looks ideal for keeping backwards compatibility with existing config files.

[wadechandler]

I would really like to support "side car" files for not just config, but for meta-data. I think that would make the content cleaner, and keep out foreign syntax. I will create a separate issue for that.

[LightGuard]

Doesn't groovy support reading YAML out of the box? If so, we wouldn't need to add any dependencies and it should be a simple fix to add it to the list of support config parsers.

[jonbullock]

It does but Groovy is an optional dependency at present and we only include the modules needed for it's template engines. Adding the YAML dependency is not a problem though. However, I assume this is in relation to #680, if so I'd prefer to keep content for output separate from the config.

[ge0ffrey]

An illustration on how it works in Awestruct (= dead project that we want to replace by JBake or Jekyll), which I created for the other image:

Source code: https://github.com/kiegroup/optaplanner-website