Code rework of placing things on walls.

Stuff goes under types.
Types have procs.
Never have 500 lines of repeated code again.

I came very close to crying while editing this. You should appreciate
that.

----

This commit entirely reworks how placing things on walls work- Posters
have intentionally been left alone to reduce the amount of lines
changed. With this commit, wall-mounted objects are no longer snowflaked
into the wall file.

code/game/objects/items/mountable_frames/apc_frame.dm

@@ -0,0 +1,29 @@
+/obj/item/mounted/frame/apc_frame
+	name = "APC frame"
+	desc = "Used for repairing or building APCs"
+	icon = 'icons/obj/apc_repair.dmi'
+	icon_state = "apc_frame"
+	mount_reqs = list("simfloor", "nospace")
+
+/obj/item/mounted/frame/apc_frame/try_build(turf/on_wall, mob/user)
+	if(..())
+		var/turf/turf_loc = get_turf(user)
+		var/area/area_loc = turf_loc.loc
+		if (area_loc.get_apc())
+			user << "<span class='rose'>This area already has an APC.</span>"
+			return //only one APC per area
+		for(var/obj/machinery/power/terminal/T in turf_loc)
+			if (T.master)
+				user << "<span class='rose'>There is another network terminal here.</span>"
+				return
+			else
+				var/obj/item/stack/cable_coil/C = new /obj/item/stack/cable_coil(turf_loc)
+				C.amount = 10
+				user << "You cut the cables and disassemble the unused power terminal."
+				qdel(T)
+		return 1
+	return
+
+/obj/item/mounted/frame/apc_frame/do_build(turf/on_wall, mob/user)
+	new /obj/machinery/power/apc(get_turf(src), get_dir(user, on_wall), 1)
+	qdel(src)