Makes Airtight ECS. (#4351)

* Makes Airtight ECS.

* Remove atmos holdovers while at it!

Content.Server/Atmos/Commands/FillGasCommand.cs

@@ -0,0 +1,45 @@
+using Content.Server.Administration;
+using Content.Server.Atmos.EntitySystems;
+using Content.Shared.Administration;
+using Content.Shared.Atmos;
+using Robust.Shared.Console;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Map;
+
+namespace Content.Server.Atmos.Commands
+{
+    [AdminCommand(AdminFlags.Debug)]
+    public class FillGas : IConsoleCommand
+    {
+        public string Command => "fillgas";
+        public string Description => "Adds gas to all tiles in a grid.";
+        public string Help => "fillgas <GridId> <Gas> <moles>";
+
+        public void Execute(IConsoleShell shell, string argStr, string[] args)
+        {
+            if (args.Length < 3) return;
+            if(!int.TryParse(args[0], out var id)
+               || !(AtmosCommandUtils.TryParseGasID(args[1], out var gasId))
+               || !float.TryParse(args[2], out var moles)) return;
+
+            var gridId = new GridId(id);
+
+            var mapMan = IoCManager.Resolve<IMapManager>();
+
+            if (!gridId.IsValid() || !mapMan.TryGetGrid(gridId, out _))
+            {
+                shell.WriteLine("Invalid grid ID.");
+                return;
+            }
+
+            var atmosphereSystem = EntitySystem.Get<AtmosphereSystem>();
+
+            foreach (var tile in atmosphereSystem.GetAllTileMixtures(gridId, true))
+            {
+                tile.AdjustMoles(gasId, moles);
+            }
+        }
+    }
+
+}