added ability set unmountable entities

src/main/java/carpet/fakes/EntityInterface.java

@@ -7,4 +7,8 @@ public interface EntityInterface
     float getMainYaw(float partialTicks);
 
     EntityEventsGroup getEventContainer();
+
+    boolean isPermanentVehicle();
+
+    void setPermanentVehicle(boolean permanent);
 }