Webservices format restriction

[MarkRS-UK]

Currently the ApiApplication object maps the format application/json to the type json (in the __construct method).

This means that incoming calls with this type can't make use of the (excellent) Jsonapi class.
Simply removing the line would allow new routes to define their own map or map json to jsonapi.
Or addFormatMap could be allowed to replace existing maps.

Would this be a useful improvement?
What say you?