Support multi file configuration and module references

[vajda]

Idea is to support definition of configuration objects in multiple files and be able to reference values across configuration files. This will provide support for implementing domain specific objects that could be packaged within jar and reused.

Configuration would look similar to the following:
userFile.yml

...
values:
  user:
    username: random(['Legolas', 'Aragorn', 'Gandalf'])
    firstName: random(['Peter', 'John', 'Mathew'])
    lastName: Smith

config.yml

...
include: userFile.yml as userFile

values:
  result:
    id: uuid()
    user: $userFile.user