Changed section data model

- Made parents nullable
- Added a data key for the tree
- Added depth for quicker layer-wise loading

I18N Commander/DataModel/Database/Common/DataContext.cs

@@ -35,6 +35,8 @@ public sealed class DataContext : DbContext
 
         modelBuilder.Entity<Section>().HasIndex(n => n.Id);
         modelBuilder.Entity<Section>().HasIndex(n => n.Name);
+        modelBuilder.Entity<Section>().HasIndex(n => n.Depth);
+        modelBuilder.Entity<Section>().HasIndex(n => n.DataKey);
 
         #endregion