FORGE-1892 and FORGE-1925

Converted contentType to multiple input type, allowing multiple media types to be supported in the resource class.

Fixed an UIInputMany issue that I ran into during testing of this feature.
And about the enumeration of all media types, I wouldn't be inclined to use all of them, since not all mediatypes would work with our generated JAX-RS resource classes. For instance, application/octet-stream is a media type in the MediaType class: http://docs.oracle.com/javaee/6/api/javax/ws/rs/core/MediaType.html and it doesn't work when specified as a mediatype in the generated resource.

That's why I've added application/xml and application/json as auto-complete options, but then the user is free to specify his own mediatypes assuming he will add the required marshallers and unmarshallers.