Upgradeable machines. (#2675)

* Start work on upgradeable machines.

* Upgradeable machines work

* Component requirements for upgradeable machines

* Better container handling

* Remember to not push submodule updates in your PRs, kids!

* Refresh parts after building a machine.

* NetSync false

* Address some reviews, fix some bugs

* Nullable stackhelpers dependencies

* Use container helper method to delete all entities in containers

* Nullable string in AddContainer

* Better examine for machine frame and construction in general

* Machine breakage

* Nullable node

* nullable GraphPrototype

* Re-save saltern for autolathe parts

* Fix SaveLoadSave

Content.Server/Interfaces/GameObjects/IRefreshParts.cs

@@ -0,0 +1,11 @@
+using System.Collections.Generic;
+using Content.Server.GameObjects.Components.Construction;
+using Robust.Shared.Interfaces.GameObjects;
+
+namespace Content.Server.Interfaces.GameObjects
+{
+    public interface IRefreshParts
+    {
+        void RefreshParts(IEnumerable<MachinePartComponent> parts);
+    }
+}