Updates storage costs

Storage cost of an item is now twice that of the next smallest item, instead of being equal to the w_class.
Items with w_class 1 or 2 are unaffected. This produces much better behaviour for containers that are limited
by storage space instead of slots, such as how toolboxes are planned to work in a future update.

code/modules/mining/ore.dm

@@ -2,6 +2,7 @@
 	name = "rock"
 	icon = 'icons/obj/mining.dmi'
 	icon_state = "ore2"
+	w_class = 2
 	var/datum/geosample/geologic_data
 	var/oretag