Drill and drone fixes

- Fixes mining drones having access to a plasma cutter energy weapon,
replaced with a diamond drill. Functionality is almost identical to what
it was with old plasma cutters.
- Pathing fixes for diamond drills.

code/modules/research/designs/mining_designs.dm

@@ -9,7 +9,7 @@
 	build_type = PROTOLATHE
 	materials = list("$metal" = 3000, "$glass" = 1000, "$diamond" = 3750) //Yes, a whole diamond is needed.
 	reliability_base = 79
-	build_path = /obj/item/weapon/pickaxe/diamonddrill
+	build_path = /obj/item/weapon/pickaxe/drill/diamonddrill
 	category = list("Mining")
 
 /datum/design/pick_diamond