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/Construction/IEdgeCondition.cs

@@ -1,4 +1,5 @@
 using System.Threading.Tasks;
+using JetBrains.Annotations;
 using Robust.Shared.Interfaces.GameObjects;
 using Robust.Shared.Interfaces.Serialization;
 using Robust.Shared.Utility;
@@ -8,6 +9,6 @@ namespace Content.Shared.Construction
     public interface IEdgeCondition : IExposeData
     {
         Task<bool> Condition(IEntity entity);
-        void DoExamine(IEntity entity, FormattedMessage message, bool inExamineRange) { }
+        bool DoExamine(IEntity entity, FormattedMessage message, bool inExamineRange) { return false; }
     }
 }