Updating Template to have a lazy master template id.

Adding a few new methods to the DataTypeService, which were needed for the import of DataTypes.
Adding bulk saving of templates.
Adding TopologicalSorter for sorting dependencies.
Implementing import of DataTypes and Templates.
Renaming the import test fixture for consistency after having creating the PackagingService.

src/Umbraco.Core/Models/Template.cs

@@ -52,7 +52,7 @@ namespace Umbraco.Core.Models
         internal string NodePath { get; set; }
 
         [DataMember]
-        internal int MasterTemplateId { get; set; }
+        internal Lazy<int> MasterTemplateId { get; set; }
 
         [DataMember]
         internal string MasterTemplateAlias { get; set; }