Adding basic Ouroboros API

A simple Ouroboros API wrapper for Shimmie.

Tested on CartonBox and follows the API output from e621 as closely as possible.
Currently only viewing a list of posts, viewing a post and listing tags works. Adding new posts is next on the line of stuff To-Do.

Yes, it's yet-another-api-for-shimmie. Yes, it only supports json output while it lies to have xml magic. No, it doesn't brew coffee... or tea (418).