Easy config using group_vars instead of role-bound vars

[lisael]

We could gather all vars in a single file, and even use string replacement to make config as simple as:

https://gist.github.com/lisael/f9af1d96b1323c56ec8c

this allow the user to keep all control over her config but also provides a sensible default config with minimal pain.

[brucespang]

Another nice thing about having a single config file is that it would make merge conflicts less likely when updating sovereign.

[al3x]

I like it. It does decrease the "modularity" of each of the roles, and it isn't in keeping with Ansible conventions, but hey rules are made to be broken ;) I'd love to see a pull request!

[gregkare]

I agree, it would be really convenient to have one global file to override configuration from all the roles. That file could even be added to .gitignore with a sample showing all the variables you can use. I'm new to Ansible but I'm going to play with overrides and see what I can do.

[gregkare]

My pull request above is a proposal using vars_files. I wanted to use group_vars but the variables from the roles had precedence, so I ended up with this. What do you think?

Obviously it needs documentation, but I don't want to document this if it's a wrong way to do this :)