Core - Fixed data model namespaces

Modules - Added IsPropertyInUse API
UI - Properly dispose data model paths wherever they are used

src/Artemis.Core/Services/Registration/DataModelService.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using Artemis.Core.DataModelExpansions;
 using Artemis.Core.Modules;
 
 namespace Artemis.Core.Services

src/Artemis.Core/Services/Registration/Interfaces/IDataModelService.cs

@@ -1,6 +1,6 @@
 using System;
 using System.Collections.Generic;
-using Artemis.Core.DataModelExpansions;
+using Artemis.Core.Modules;
 
 namespace Artemis.Core.Services
 {