Important bug fixes for edit/commit (extended property check) (#294)

* Ensures that metadata is "extended" before creating a new row edit object
* Adds the commit handler to edit data service initialization calls
* Unit tests for the associated changes

src/Microsoft.SqlTools.ServiceLayer/EditData/UpdateManagement/RowEdit.cs

@@ -38,6 +38,11 @@ namespace Microsoft.SqlTools.ServiceLayer.EditData.UpdateManagement
         /// <param name="associatedMetadata">Metadata provider for the object to edit</param>
         protected RowEditBase(long rowId, ResultSet associatedResultSet, EditTableMetadata associatedMetadata)
         {
+            if (!associatedMetadata.HasExtendedProperties)
+            {
+                throw new ArgumentException(SR.EditDataMetadataNotExtended);
+            }
+
             RowId = rowId;
             AssociatedResultSet = associatedResultSet;
             AssociatedObjectMetadata = associatedMetadata;