Start/Stop operations should map to Enable/Disable transmission on RPG

The Start and Stop operations are enabled (i.e. clickable in the Operate palette) for remote process groups (RPG) but these actions have no impact. Rather, the valid operations for RPGs are Enable transmission and Disable transmission, which must be selected from the context menu on the component.

The Start/Stop actions should invoke the respective operation on the RPG so that selecting a segment containing both processors and RPG and choosing Start/Stop from the Operate palette has the intended outcome (i.e. starting or stopping all selected components, including enabling/disabling transmission for the RPG(s)).