Make Scenery a domain aggregate with no I/O

Parsing and loading move to Infrastructure/Sceneries. Weather becomes a value
object owning the "does this differ from the file" rule.

StarterNG/Domain/Consist.cs

@@ -4,6 +4,7 @@ using System.Collections.Generic;
 using System.Linq;
 
 using StarterNG.Classes;
+using StarterNG.Domain.Sceneries;
 
 namespace StarterNG.Domain;