Adds snake people (#2029)

Changes:
-adds snake people as a whitelisted species
-adds tail mechanics, ported from europa station, to the snake people, you can coil it up, people can attack it, stomp the tail and etc
-snake people can spit poison
-snake people can't use shoes
-snake people also have some other features like having a minor brute resist, claws and cuff breaking
-snake people can have different scale colors and eyes colors, but green is the best color without doubt
-also adds snake people

code/modules/projectiles/projectile/energy.dm

@@ -232,3 +232,15 @@
 	kill_count = 75
 	embed = 0
 	incinerate = 10*/
+
+/obj/item/projectile/energy/venom
+	name = "venom spit"
+	icon_state = "neurotoxin"
+	damage = 10
+	damage_type = TOX
+	
+/obj/item/projectile/energy/venom/on_hit(var/atom/target, var/blocked = 0)
+	if(ishuman(target))
+		var/mob/living/carbon/human/M = target
+		if(M.reagents)	M.reagents.add_reagent("toxin", 5)
+	..()