Decal Placer + add new decals for mapping (#6548)

* abomination

* okay its less unabashedly garbage now

* other UI changes

* its britney bitch

* proper greyscale full/half/quarter tiles

* misc cleanup

* rsi

* Add a palette system. It's Kara's problem now.

* oops

* a

* Departmental palette alpha tweaks

* oopy

* so true

* Update Content.Shared/Decals/ColorPalettePrototype.cs

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>

* fixes for that

* neutral light color and new warning lines

* dirt

* checkerboards

* oop

Co-authored-by: moonheart08 <moonheart08@users.noreply.github.com>
Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>

Content.Shared/Decals/SharedDecalSystem.cs

@@ -8,6 +8,7 @@ using Robust.Shared.IoC;
 using Robust.Shared.Map;
 using Robust.Shared.Maths;
 using Robust.Shared.Prototypes;
+using Robust.Shared.Serialization;
 
 namespace Content.Shared.Decals
 {
@@ -150,4 +151,31 @@ namespace Content.Shared.Decals
             return _xIndex <= _chunkRT.X;
         }
     }
+
+    /// <summary>
+    ///     Sent by clients to request that a decal is placed on the server.
+    /// </summary>
+    [Serializable, NetSerializable]
+    public sealed class RequestDecalPlacementEvent : EntityEventArgs
+    {
+        public Decal Decal;
+        public EntityCoordinates Coordinates;
+
+        public RequestDecalPlacementEvent(Decal decal, EntityCoordinates coordinates)
+        {
+            Decal = decal;
+            Coordinates = coordinates;
+        }
+    }
+
+    [Serializable, NetSerializable]
+    public sealed class RequestDecalRemovalEvent : EntityEventArgs
+    {
+        public EntityCoordinates Coordinates;
+
+        public RequestDecalRemovalEvent(EntityCoordinates coordinates)
+        {
+            Coordinates = coordinates;
+        }
+    }
 }