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/organs/subtypes/xenos.dm

@@ -104,3 +104,39 @@
 	name = "skull"
 	dislocated = -1
 	vital = 0
+
+/obj/item/organ/external/groin/snake
+	name = "tail"
+	max_damage = 200
+	min_broken_damage = 160
+	body_hair = "markings"
+
+/obj/item/organ/external/head/snake
+	body_hair = "markings"
+
+/obj/item/organ/external/chest/snake
+	body_hair = "markings"
+
+/obj/item/organ/venomgland
+	name = "venom gland"
+	desc = "Oversized glands, filled with a venomous liquid."
+	parent_organ = "head"
+	icon = 'icons/effects/blood.dmi'
+	icon_state = "xgibtorso"
+	organ_tag = "venom gland"
+	
+/obj/item/organ/venomgland/process()
+	if (is_broken())
+		owner.verbs -= /mob/living/carbon/human/proc/venomspit
+		owner << "<span class='notice'> Your fangs dries as the glands are crushed by the violence!</span>"
+	..()
+
+/obj/item/organ/venomgland/replaced(var/mob/living/carbon/human/target)
+	owner.verbs += /mob/living/carbon/human/proc/venomspit
+	owner << "<span class='notice'> Venom runs through your fangs!</span>"
+	..()
+
+/obj/item/organ/venomgland/removed(var/mob/living/carbon/human/target)
+	target.verbs -= /mob/living/carbon/human/proc/venomspit
+	target << "<span class='warning'>Your fangs dries as the glands are torn away from you.</span>"
+	..()