Add back menu discard string

    <!-- Confirmation dialog contents after users selects to delete a Writable contact. -->

    <string name="deleteConfirmation">This contact will be deleted.</string>

    <!-- Menu item to indicate you want to stop editing a contact and NOT save the changes you've made [CHAR LIMIT=30] -->

    <string name="menu_discard">Discard changes</string>

    <!-- Message displayed in a toast when you try to view the details of a contact that

         for some reason doesn't exist anymore. [CHAR LIMIT=NONE]-->

    <string name="invalidContactMessage">The contact doesn\'t exist.</string>