New Swagger generation options

Add new options to Swagger spec generation

• Option to add GoogleJsonError as default response body
• Option to add GoogleJsonError for specific error code when a method
  throws a well-known subclass of ServiceException
• Option to extract common parameters at path level
• Option to extract named parameters at spec level
• Provide a way to customize title and description in info section

Swagger fixes

• Add scope in security definitions (current spec is not valid)
• Swagger should return 204 on response without body