Data model nodes - Only allow picking data model entries of types supported by nodes

Data models - Fixed path registration not registering two paths pointing to the same property twice (fixes data model-reliant node scripts that stop updating)

src/Artemis.Core/Plugins/Modules/DataModel.cs

@@ -345,8 +345,8 @@ public abstract class DataModel
     {
         lock (_activePaths)
         {
-            if (_activePaths.Contains(path))
-                return;
+            if (_activePaths.Any(p => ReferenceEquals(p, path)))
+                throw new ArtemisCoreException("Path already present on this data model, initialization done twice?");
 
             _activePaths.Add(path);