Document unused fields in PHCorePhilHealthID and PHCorePddRegistration

[jgsuess]

Feedback / Comments:
the PHCorePhilHealthID and PHCorePddRegistration should nail down the fields that aren't going to be used

Submitter: Grahame Grieve

[jgsuess]

Notes:
For consideration.

[jgsuess]

Unnamed: 6:
For discussion in DH TWG