Add Ghoat and update warthog/pumba

- The Ghoat animal is passive, he eats flowers on his way, drop raw_meat if you kill it. But be carful, if you attack him, he will hit you back ! (like cow/warthog and other passive monster who can defend himself)
- Warthogs now spawn on default:dirt and default:junglegrass, this change is made because we move progressively the warthog in jungle

mods/mobs/cow.lua

@@ -9,7 +9,7 @@ mobs:register_mob("mobs:cow", {
 	attack_type = "dogfight",
 	damage = 5,
 	-- health & armor
-	hp_min = 20,
+	hp_min = 25,
 	hp_max = 30,
 	armor = 200,
 	-- textures and model