Admin-only price set fields should be available from contact page

CRM-5766 created "admin-only" price set fields available in civicrm/participant/add and civicrm/contribute/add.

However, these price set fields are not available when you view a particular contact and click either "Add Event Registration" or "Record Contribution".

This would be particularly helpful when submitting CC data and the contact billing address is in the db (avoiding having to solicit and re-type the address).