Adds Radio Jammers to Traitor Uplink

Subspace Jammers can be bought in the traitor uplink for 25 TC.  They are already in the code, but this PR adds them to the uplink.

This PR also adds a power meter to the sprite, as a small QoL change.

They run off of weapon cells and one cell will last for about a minute.

code/game/objects/items/devices/radio/jammer.dm

@@ -19,16 +19,18 @@ var/global/list/active_radio_jammers = list()
 	icon = 'icons/obj/device.dmi'
 	icon_state = "jammer0"
 	var/active_state = "jammer1"
+	var/last_overlay_percent = null // Stores overlay icon_state to avoid excessive recreation of overlays.
 
 	var/on = 0
 	var/jam_range = 7
 	var/obj/item/weapon/cell/device/weapon/power_source
-	var/tick_cost = 80
+	var/tick_cost = 80 // Will last for roughly one minute, as process() ticks every 2 seconds.
 
 	origin_tech = list(TECH_ILLEGAL = 7, TECH_BLUESPACE = 5) //Such technology! Subspace jamming!
 
 /obj/item/device/radio_jammer/New()
 	power_source = new(src)
+	update_icon() // So it starts with the full overlay.
 
 /obj/item/device/radio_jammer/Destroy()
 	if(on)
@@ -42,7 +44,7 @@ var/global/list/active_radio_jammers = list()
 	processing_objects.Remove(src)
 	active_radio_jammers -= src
 	on = FALSE
-	icon_state = initial(icon_state)
+	update_icon()
 
 /obj/item/device/radio_jammer/proc/turn_on(mob/user)
 	if(user)
@@ -50,7 +52,7 @@ var/global/list/active_radio_jammers = list()
 	processing_objects.Add(src)
 	active_radio_jammers += src
 	on = TRUE
-	icon_state = active_state
+	update_icon()
 
 /obj/item/device/radio_jammer/process()
 	if(!power_source || !power_source.check_charge(tick_cost))
@@ -60,6 +62,7 @@ var/global/list/active_radio_jammers = list()
 		turn_off(notify)
 	else
 		power_source.use(tick_cost)
+		update_icon()
 
 
 /obj/item/device/radio_jammer/attack_hand(mob/user)
@@ -86,4 +89,25 @@ var/global/list/active_radio_jammers = list()
 		power_source.update_icon() //Why doesn't a cell do this already? :|
 		user.unEquip(power_source)
 		power_source.forceMove(src)
+		update_icon()
 		to_chat(user,"<span class='notice'>You insert \the [power_source] into \the [src].</span>")
+
+/obj/item/device/radio_jammer/update_icon()
+	if(on)
+		icon_state = active_state
+	else
+		icon_state = initial(icon_state)
+
+	var/overlay_percent = 0
+	if(power_source)
+		overlay_percent = between(0, round( power_source.percent() , 25), 100)
+	else
+		overlay_percent = 0
+
+	// Only Cut() if we need to.
+	if(overlay_percent != last_overlay_percent)
+		overlays.Cut()
+		var/image/I = image(src.icon, src, "jammer_overlay_[overlay_percent]")
+		overlays += I
+		last_overlay_percent = overlay_percent
+