Deletes the mapping for the given bundle from the database.
$type: The entity type the mapping refers to.
$bundle: The bundle the mapping refers to.
Return boolean TRUE if mapping deleted, FALSE if not.
function rdf_mapping_delete($type, $bundle) {
$num_rows = db_delete('rdf_mapping')
->condition('type', $type)
->condition('bundle', $bundle)
->execute();
return (bool) ($num_rows > 0);
}