Much nicer syringe gun implementation

Makes syringe guns a type of launcher gun, and removes the hack
projectile.
Also moves syringe and dart gun source files into the modules/projectile
folder.

code/defines/obj/weapon.dm

@@ -67,7 +67,7 @@
 	icon_state = "bike_horn"
 	item_state = "bike_horn"
 	throwforce = 3
-	w_class = 1.0
+	w_class = 2
 	throw_speed = 3
 	throw_range = 15
 	attack_verb = list("HONKED")