This is a minor matter, but since I changed the behavior I wanted to throw it out:

Below in "the_value_for", I flattened these two if statements into one.  I check first for the hidden "clear" value, **then** I check for the file type, and then I just return the value.  Above, the "hidden" logic is limited to only the field types.

My reasons for making this change are

1.  I don't think it matters, as most fields are not going to attempt to set a -hidden field.
2.  Keeping it exposed to all will allow it to be used by new field types in the future -- without modifying the guts of this app for a new field type later.