Adds New PoI Features + Bonus PoI (#5796)

* Adds cliffs.

* Finishes lava and polishes the other things.

* Hopefully finished with all the new shinies.

code/modules/vehicles/vehicle.dm

@@ -164,6 +164,10 @@
 	..()
 	healthcheck()
 
+/obj/vehicle/proc/adjust_health(amount)
+	health = between(0, health + amount, maxhealth)
+	healthcheck()
+
 /obj/vehicle/ex_act(severity)
 	switch(severity)
 		if(1.0)