Add ability to document API operations that support multiple content type responses
- relevant 'supportedContentTypes' field will be renamed to 'produces' in 1.2 spec (release not imminent)
- default behaviour if no 'produces' specified is to return 'application/json' as this is current behaviour of swagger-ui
Merge pull request #272 from caoilte/2.2.x_2.9

Add ability to document API operations that support multiple content type responses
Remove unnecessary servlet mappings.
Fix url() invocation to includeServletPath = false.
scalatra-auth doesn't need to depend on scalatra-commands, fixes #274
Credits and notes.
Merge branch '2.2.x_2.9' into 2.2.x_2.10