PD CodeSystems have URL mismatch with canonical URL

[robeastwood-agency]

In preparation for transition to the external template methodology (via #33), it is evident that the 2 PD CodeSystems have a non-standard URL -

QA errors

codesystem-endpoint-payload-type.xml: the canonical URL (http://hl7.org.au/fhir/pd/CodeSystem/endpoint-payload-type) does not match the URL (http://hl7.org.au/fhir/CodeSystem/endpoint-payload-type)
codesystem-smd-interfaces.xml: the canonical URL (http://hl7.org.au/fhir/pd/CodeSystem/smd-interfaces) does not match the URL (http://hl7.org.au/fhir/CodeSystem/smd-interfaces)

Essentially the CodeSystem URLs have the prefix http://hl7.org.au/fhir/<resource> whereas the PD ValueSet, StructureDefinition and ImplementationGuide resources all have the prefix http://hl7.org.au/fhir/pd/<resource>.

Given the downstream implementation impact of changing CodeSystem URLs, it is unlikely that these will be changed. However, suggest that the QA errors be eliminated by adding special-url parameters in the ImplementationGuide resource, as follows:

<parameter>
      <code value="special-url"/>
      <value value="http://hl7.org.au/fhir/CodeSystem/endpoint-payload-type"/>
</parameter>
<parameter>
      <code value="special-url"/>
      <value value="http://hl7.org.au/fhir/CodeSystem/smd-interfaces"/>
</parameter>