Add utility AI (#806)

Co-authored-by: Pieter-Jan Briers <pieterjan.briers@gmail.com>
Co-authored-by: Metal Gear Sloth <metalgearsloth@gmail.com>
Co-authored-by: Pieter-Jan Briers <pieterjan.briers+git@gmail.com>

Content.Server/AI/WorldState/States/Combat/WeaponEntityState.cs

@@ -0,0 +1,16 @@
+using JetBrains.Annotations;
+using Robust.Shared.Interfaces.GameObjects;
+
+namespace Content.Server.AI.WorldState.States.Combat
+{
+    [UsedImplicitly]
+    public sealed class WeaponEntityState : PlanningStateData<IEntity>
+    {
+        // Similar to TargetEntity
+        public override string Name => "WeaponEntity";
+        public override void Reset()
+        {
+            Value = null;
+        }
+    }
+}