This method will delete a custom field.
|business_code||Integer||This is the business we are working within.|
|mod_time||Timestamp||This is the modification time of your data so we can verify it hasn't changed since it was downloaded.|
|custom_field_id||Integer||This is the id of the custom field we want to update.|
|format||enumeration||(optional) Set this value to "xml" for XML raw formatted output, "xml-clean" for XML tidy formatted output or "json" for JSON formatted output. If not passed, "xml" is used as a default|