Add fields and states required for robust Volkswagen safety compliance (

#8)

* Add fields and states required for robust Volkswagen safety compliance.

* Add generic (manufacturer-independent) cruise-control button events in support of enhanced steering wheel or third stalk ACC control.
* Add generic (manufacturer-independent) gearshift position definitions for Eco and Manumatic.
* Add preEntry Event state, in support of generic (manufacturer-independent) strict safety model compliance. This is intended for later use in controlsd, to display NO_ENTRY alerts without attempting engagement.
* Update Volkswagen safety model ID from "vw" to "volkswagen" to be consistent with the existing community port.

* Remove the separate increase and decrease buttons.

A different approach has been discussed and agreed to.

* Per conversation with Riccardo, pulling the preEntry thing until later.

car.capnp

@@ -166,6 +166,8 @@ struct CarState {
     sport @5;
     low @6;
     brake @7;
+    eco @8;
+    manumatic @9;
   }
 
 
@@ -184,6 +186,9 @@ struct CarState {
       altButton1 @6;
       altButton2 @7;
       altButton3 @8;
+      setCruise @9;
+      resumeCruise @10;
+      gapAdjustCruise @11;
     }
   }
 }