Removing reserved fields from the grammar and adding them back

[mettta]

When you add a reserved field that is not in the grammar, it is shown at the end of the list of fields in the form. It should be shown in its place.

This was in the Rationale example.

Question: if the document grammar does not include reserved fields, they should be present in the form and be available for processing as existing fields in the grammar. It should not be possible to delete reserved fields or change their position, no exceptions.

[mettta]