Extend controller lookup to subfolders

[tracend]

Although having a one level deep controller stack is a clean convention, and a limitation that helps for a cleaner route table, there are cases (especially in plugins) where some controller needs to be nested.

For example, the [twitter] module may have links that belong under the api namespace. So a request to the twitter api may look like:

/api/twitter/[request/uri]

The controller that accepts those requests needs to live either in an api folder or be named api-twitter.js.

Either convention should have the same effect.