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.Client/GameObjects/Components/Disposal/DisposalUnitComponent.cs

@@ -4,6 +4,7 @@ using Robust.Shared.GameObjects;
 namespace Content.Client.GameObjects.Components.Disposal
 {
     [RegisterComponent]
+    [ComponentReference(typeof(SharedDisposalUnitComponent))]
     public class DisposalUnitComponent : SharedDisposalUnitComponent
     {
     }