Create a validator library for Measurement.Result messages

[SanjayVas]

This came up from the investigation of #1858, which turned out to be caused by an EDP calling FulfillDirectRequisition with a Measurement.Result missing a required field. Since the message is encrypted, it cannot be validated by the service method.

A validation library that can used by EDPs on the plaintext result would be helpful to prevent cases like this. It should also be used by the Reporting system after the message is decrypted so that the validation is consistent.