New Step Device

John Friede of HWH Corporation submits the attached DGNs for a Step device.

The Step Control device shall have a DSA of 147, in the Mechanical Components group.

The STEP_STATUS message shall have DGN 1FE89h
The STEP_COMMAND message shall have DGB 1FE88h

A set of SPNs from the author is forthcoming.

Justification: Steps are sufficiently different from a slide room, with different behaviors and often additional sensors, to justify a new message structure. The additional DSA will make service more intuitive.