Ports advanced shield generators from Baystation

- Creates new advanced shield generators, designed to replace old hull and bubble shield generators.
- Upgrades the floor mounted and handheld shield diffusers.
- Makes underfloor shield diffusers actually constructable.
- Handheld diffusers orderable via uplink.
- Removes supply packs and research datums  for the old generators, but leaves their code in place for maps that still use them.
- Integrates with the meteor and electrical storm events.
- Integrates with mob AI (they know how to attack it)

code/modules/shieldgen/shield_diffuser.dm

@@ -4,6 +4,7 @@
 	description_info = "This device disrupts shields on directly adjacent tiles (in a + shaped pattern). They are commonly installed around exterior airlocks to prevent shields from blocking EVA access."
 	icon = 'icons/obj/machines/shielding.dmi'
 	icon_state = "fdiffuser_on"
+	circuit = /obj/item/weapon/circuitboard/shield_diffuser
 	use_power = USE_POWER_ACTIVE
 	idle_power_usage = 25		// Previously 100.
 	active_power_usage = 500	// Previously 2000
@@ -13,12 +14,17 @@
 	var/alarm = 0
 	var/enabled = 1
 
-/obj/machinery/shield_diffuser/New()
-	..()
+/obj/machinery/shield_diffuser/Initialize()
+	. = ..()
+	// TODO - Remove this bit once machines are converted to Initialize
+	if(ispath(circuit))
+		circuit = new circuit(src)
+	default_apply_parts()
+
 	var/turf/T = get_turf(src)
 	hide(!T.is_plating())
 
-//If underfloor, hide the cable
+//If underfloor, hide the cable^H^H diffuser
 /obj/machinery/shield_diffuser/hide(var/i)
 	if(istype(loc, /turf))
 		invisibility = i ? 101 : 0
@@ -38,6 +44,9 @@
 		return
 	for(var/direction in cardinal)
 		var/turf/simulated/shielded_tile = get_step(get_turf(src), direction)
+		for(var/obj/effect/shield/S in shielded_tile)
+			S.diffuse(5)
+		// Legacy shield support
 		for(var/obj/effect/energy_field/S in shielded_tile)
 			qdel(S)
 
@@ -50,16 +59,27 @@
 	else
 		icon_state = "fdiffuser_on"
 
-/obj/machinery/shield_diffuser/attack_hand()
+/obj/machinery/shield_diffuser/attack_hand(mob/user as mob)
+	if((. = ..()))
+		return
 	if(alarm)
-		to_chat(usr, "You press an override button on \the [src], re-enabling it.")
+		to_chat(user, "You press an override button on \the [src], re-enabling it.")
 		alarm = 0
 		update_icon()
 		return
 	enabled = !enabled
 	update_use_power(enabled ? USE_POWER_ACTIVE : USE_POWER_IDLE)
 	update_icon()
-	to_chat(usr, "You turn \the [src] [enabled ? "on" : "off"].")
+	to_chat(user, "You turn \the [src] [enabled ? "on" : "off"].")
+
+/obj/machinery/shield_diffuser/attackby(var/obj/item/W, var/mob/user)
+	if(default_deconstruction_screwdriver(user, W))
+		return
+	if(default_deconstruction_crowbar(user, W))
+		return
+	if(default_part_replacement(user, W))
+		return
+	return ..()
 
 /obj/machinery/shield_diffuser/proc/meteor_alarm(var/duration)
 	if(!duration)
@@ -71,4 +91,4 @@
 	. = ..()
 	to_chat(user, "It is [enabled ? "enabled" : "disabled"].")
 	if(alarm)
-		to_chat(user, "A red LED labeled \"Proximity Alarm\" is blinking on the control panel.")
+		to_chat(user, "A red LED labeled \"Proximity Alarm\" is blinking on the control panel.")