Clear field values when removing a schema

Scenario:

1. Add a facet to a document (which adds a schema)
2. Save a value in one of the schema fields
3. (later) Change the value, Remove the facet, save the document
4. (even later) add the facet back

The old field value is still there (step 2) not the new one from step 3.

According to Florent there is code in DBS to deal with this, but not VCS, so he asked me to file a ticket.