consolidate description of Response/@Returncode

C Return Values
The following list defines the standard return codes for messaging. Return code values are SHALL beintegers. Error values below
100 are reserved for protocol errors. Error values above 100 are SHALL be used for device and controller errors, while those higher
than 200 refer to job and pipe specific errors.
Implementations SHOULD supply values from this list. If no approriate return code exists in this list, proprietary return codes MAY be provided and SHOULD have values above 1000.

<make description (NOT the default!) unconditional>
remove change flags from appendix return codes - they are an open list and thus not tracked.