Changes to comply with Swagger spec and add support for multiple response types (e.g. application/xml) in Swagger-UI
Merge pull request #290 from JoelRSimpson/master

Allow additional response type (e.g. application/xml) support in Swagger-UI
Improves Forms to provide improved CSRF protection by having different form key for each http method and url
Optimises Forms to remove the redundant title static method and its usage
Let Forms use Scope to get reference of restler for its static methods
Let Forms use a const for the form key name
Improves HtmlFormat to include form_key method for twig templates to generate CSRF token (form_key) for your custom forms