Scribe Annotations

[jbrooksuk]

This PR annotates the API controllers in a way that we can use Scribe to generate the API documentation.

1. I'm currently using Scribe within the cachethq/cachet application itself to generate the documentation. For this to work, I've had to override each model's newFactory method to return the correct class.
2. I've updated all endpoint docblocks to use Scribe's PHP annotations (we can't use the attribute syntax, since Scribe isn't in the core itself).

At some point, I'm going to automate all of this in the main repo itself.