Separates the sharp flag into edge and sharp

Now weapons can properly cause cuts without necessarily having a greater
chance to remove limbs.

Also separates is_sharp, has_edge, and can_puncture.

code/defines/obj/weapon.dm

@@ -228,6 +228,7 @@
 	icon = 'icons/obj/shards.dmi'
 	icon_state = "large"
 	sharp = 1
+	edge = 1
 	desc = "Could probably be used as ... a throwing weapon?"
 	w_class = 2.0
 	force = 5.0