Adds the can_charge var to energy guns

If set to 0, makes it so the gun cannot be charged in recharges. Set to
1 by default, only the nuclear (AKA advanced) egun and both plasma
cutters have it set to 0. (Nuclear egun was previously unable to be
charged, but used an istype check specific to it.)

code/game/machinery/recharger.dm

@@ -29,14 +29,18 @@
 			user << "\red The [name] blinks red as you try to insert the item!"
 			return
 
-		if (istype(G, /obj/item/weapon/gun/energy/gun/nuclear))
-			user << "<span class='notice'>Your gun's recharge port was removed to make room for a miniaturized reactor.</span>"
-			return
+		if (istype(G, /obj/item/weapon/gun/energy))
+			var/obj/item/weapon/gun/energy/E = G
+			if(!E.can_charge)
+				user << "<span class='notice'>Your gun has no external power connector.</span>"
+				return
+
 		if(istype(G, /obj/item/device/laptop))
 			var/obj/item/device/laptop/L = G
 			if(!L.stored_computer.battery)
 				user << "There's no battery in it!"
 				return
+
 		user.drop_item()
 		G.loc = src
 		charging = G

code/modules/projectiles/guns/energy.dm

@@ -9,6 +9,7 @@
 	var/cell_type = "/obj/item/weapon/stock_parts/cell"
 	var/projectile_type = "/obj/item/projectile/beam"
 	var/modifystate
+	var/can_charge = 1
 
 	emp_act(severity)
 		power_supply.use(round(power_supply.charge / severity))

code/modules/projectiles/guns/energy/nuclear.dm

@@ -46,6 +46,7 @@
 	var/lightfail = 0
 	var/charge_tick = 0
 	can_flashlight = 0
+	can_charge = 0
 
 	New()
 		..()

code/modules/projectiles/guns/energy/special.dm

@@ -307,6 +307,7 @@ modules/mob/living/carbon/human/life.dm if you die, you will be zoomed out.
 	charge_cost = 250
 	fire_delay = 10
 	icon_override = 'icons/mob/in-hand/guns.dmi'
+	can_charge = 0
 
 /obj/item/weapon/gun/energy/plasmacutter/examine(mob/user)
 	..()