* SenecaII-base.xml (menu): add Route Manager to the Seneca menu.
* Systems/kcs55.{nas,xml}: when "Link NAV1 to GPS" is enabled in the GPS dialog,
feed the GPS desired course and CDI deflection into the NAV1 instrument and
feed the distance to waypoint, time to waypoint and groundspeed to the DME instrument
if it is switched on and selects NAV1 as the source.
This makes it possible to follow a GPS route in the SenecaII. The cockpit does not have any
visible GPS yet; the only way to use this feature is by using the FlightGear dialogs,
"Seneca > Route Manager" and "Equipment > GPS".
