Adds Response.created methods

[grosch]

Provides convenience methods for returning newly created objects. Sets the status code to 201 (Created) and includes the Location header.

func create(req: Request) throws -> EventLoopFuture<Response> {
    let todo = try req.content.decode(Todo.self)
    return todo.create(on: req.db).flatMapThrowing {
        try .created(todo, for: req)
    }
}

[grosch]

Hold off on this...I'm making some other changes here.

[grosch]

Resubmitting a new request