The disposals pushing and pulling update (#1875)

* Add collision to disposal unit and pipes
Make disposal unit and pipes pullable
Implement proper handling of collisions in disposals

* Implement IsExiting
Move DisposalSystem to shared

* Change SharedDisosalUnitComponent to call manager.ContainsEntity directly

* Update saltern.yml

Co-authored-by: Julian Giebel <j.giebel@netrocks.info>

Content.Shared/GameObjects/EntitySystems/SharedDisposalUnitSystem.cs

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