Move passenger-handling to Entity

src/main/java/org/bukkit/entity/Entity.java

@@ -109,4 +109,34 @@ public interface Entity {
      * @return Server instance running this Entity
      */
     public Server getServer();
+
+    /**
+     * Gets the primary passenger of a vehicle. For vehicles that could have
+     * multiple passengers, this will only return the primary passenger.
+     * 
+     * @return an entity
+     */
+    public abstract Entity getPassenger();
+
+    /**
+     * Set the passenger of a vehicle.
+     * 
+     * @param passenger
+     * @return false if it could not be done for whatever reason
+     */
+    public abstract boolean setPassenger(Entity passenger);
+
+    /**
+     * Returns true if the vehicle has no passengers.
+     * 
+     * @return
+     */
+    public abstract boolean isEmpty();
+
+    /**
+     * Eject any passenger. True if there was a passenger.
+     * 
+     * @return
+     */
+    public abstract boolean eject();
 }