Create a config file spec for watchmaker

[lorengordon]

Right now, the config file is really a list of workers and worker configs. Running into a couple issues with this approach:

1. There isn't really a way to specify options for watchmaker itself, such as the proposed version constraint option, without getting wrapped up in how worker configs are loaded.
2. There is no way to process a config other than just running the worker. It would help to have a method that validates the config or sets defaults or deprecates options...

[ferricoxide]

This issue is pretty old: can it be closed/is it "OBE"?

[lorengordon]

Still valid