Route generation with URL patterns

Route generation will now inspect method signatures in APIHandlers and ViewHandlers, and construct routes with URL patterns based on the signatures. URL patterns match [a-zA-Z0-9_]+.

Backwards Compatibility: body is no longer provided by io_schema as the sole argument to HTTP methods. Any existing code using body can now use self.body to get the same object.

Input and output example fields

• Add input_example and output_example fields
• status_code 400 on ValidationError
• Exclude delete from input validation