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.Shared/GameObjects/Components/Construction/MachineFrameVisuals.cs

@@ -0,0 +1,10 @@
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.GameObjects.Components.Construction
+{
+    [NetSerializable]
+    public enum MachineFrameVisuals
+    {
+        State,
+    }
+}