Airlock / firelock code refactor, pseudo-prediction implementation (#3037)

* splits off airlocks, firelocks

* adds airlock prediction. anims broken though

* fixes animation weirdness

* removes opacity prediction because it looked odd

* Now firelocks don't visually start open. Argh.

* Fixes firelock weirdness, saneifies _state var.

* Documentation changes, code shuffle.

* Lets firelocks crush people.

* Stops open-hand opening/closing firelocks.

* updates serializable, netserializable attributes

* Addresses reviews... hopefully.

* updates submodule?

* nullability

* fuck fuck fuck fuck

* fucking finally

Content.Server/GameObjects/EntitySystems/ServerDoorSystem.cs

@@ -0,0 +1,44 @@
+#nullable enable
+using JetBrains.Annotations;
+using Robust.Shared.GameObjects;
+
+namespace Content.Server.GameObjects.EntitySystems
+{
+    /// <summary>
+    /// Used on the server side to manage global access level overrides.
+    /// </summary>
+    class ServerDoorSystem : EntitySystem
+    {
+        /// <summary>
+        ///     Determines the base access behavior of all doors on the station.
+        /// </summary>
+        public AccessTypes AccessType { get; set; }
+
+        /// <summary>
+        /// How door access should be handled.
+        /// </summary>
+        public enum AccessTypes
+        {
+            /// <summary> ID based door access. </summary>
+            Id,
+            /// <summary>
+            /// Allows everyone to open doors, except external which airlocks are still handled with ID's
+            /// </summary>
+            AllowAllIdExternal,
+            /// <summary>
+            /// Allows everyone to open doors, except external airlocks which are never allowed, even if the user has
+            /// ID access.
+            /// </summary>
+            AllowAllNoExternal,
+            /// <summary> Allows everyone to open all doors. </summary>
+            AllowAll
+        }
+
+        public override void Initialize()
+        {
+            base.Initialize();
+
+            AccessType = AccessTypes.Id;
+        }
+    }
+}