Capability Statement format mimetype validations

[brianpos]

The new validator does not pass CapabilityStatement instances that have the format xml or json without the application/ prefix.
Refer to spec for this...
https://build.fhir.org/capabilitystatement-definitions.html#CapabilityStatement.format

https://build.fhir.org/valueset-capability-format-type.html

Should also review the set that are referenced here too:
https://hl7.org/fhir/r4b/valueset-mimetypes.html
(Gino is logging this against the spec to work out if the core spec should be clarified here, as there are differences - and I'll rechcek the java validator to see if that has a rule around these specific values too)