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/Localization/sr.xlf

@@ -601,6 +601,11 @@
         <target state="new">NULL</target>
         <note></note>
       </trans-unit>
+      <trans-unit id="EditDataMetadataNotExtended">
+        <source>Table metadata does not have extended properties</source>
+        <target state="new">Table metadata does not have extended properties</target>
+        <note></note>
+      </trans-unit>
     </body>
   </file>
 </xliff>