Remove Deprecated _body and _subject Fields

CoEnrollmentFlow and CoExpirationPolicy *_body and *_subject fields are deprecated following the introduction of Message Templates. Remove them (after v1.1.0, possibly as a v2.0.0 item).

This probably requires a task in UpgradeShell to migrate remaining values to templates, and then a later version to remove them from schema.xml. Alternately, if done as part of v2.0.0, migration could be done as part of a "run this on your v1.x instance before upgrading to v2.0" task.