Adds sized (S, M, L) power cells and a generic component for battery powered items (#2352)

* Refactor battery/powercell assets and add new ones.

* committing before I fuck things up

* slot component doned I think

* dictionary update

* Fixes

* Moving flashlight to powerslotcomponent

* har har i am using the message tubes

* Better documentation comment

* Reverting this overengineered garbage.

* Off with ye I said

* Examine texts.

* Some minor fixes to IDE complaints

* slot size from yaml

* Ignored component + removing a useless typo entry

* Making stunbatons use this

* Handle the message and remove some unnecessary dirtiness

* actionblocker checks

* remove unused file

* remove updatevisual

* make these nullable

* make these nullable too

* Unrename sprite folder

* check itemcomponent on insertion

* Use SendMessage over Owner.SendMessage

* Add support for auto-recharging batteries, an auto-recharging cell, and make flashlight status update correctly if one is inserted in it.

* get rid of public fields which are Bad

* add a description for the stun baton while i'm in here

* one more public field

* Add the blinky animation to the atomic cell

* Fix the charge indicator being STUPID

* better comments

* this is a better function

* add pause for flashlight, remove unnecessary imports from battery

* potato battery copyright link

* WHO DID THAT

* mr clean has come

* Random pitch

* pausing

* round to nearest levels

Content.Server/GameObjects/EntitySystems/BatterySystem.cs

@@ -0,0 +1,18 @@
+using Content.Server.GameObjects.Components.Power;
+using JetBrains.Annotations;
+using Robust.Shared.GameObjects.Systems;
+
+namespace Content.Server.GameObjects.EntitySystems
+{
+    [UsedImplicitly]
+    public class BatterySystem : EntitySystem
+    {
+        public override void Update(float frameTime)
+        {
+            foreach (var comp in ComponentManager.EntityQuery<BatteryComponent>(false))
+            {
+                comp.OnUpdate(frameTime);
+            }
+        }
+    }
+}