Language Packs: Many many fixes such as:

- Add a "Update Translations" stand-alone button to the updates page
- Shift Language feedback to before update process completion action links & limit the verbosity of output (name + success/errors)
- Simplify/combine the language update descriptive string to only include a plugin/theme name
- Properly handle cache clearing after language updates to prevent langs being repeditively updated
- Display a "All items up to date" string when there's nothing to do
- Reduce the 'Connection Information' from a <h2> to a <h3> to remove duplicate h2's and screen icons from update screens
- Fix the Direct filesystem method not being used for Language updates because WP_LANG_DIR doesn't exist (check it's parent for writable instead)
See #18200, #22704



git-svn-id: https://develop.svn.wordpress.org/trunk@25806 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/update-core.php

@@ -889,6 +889,9 @@ function update_core($from, $to) {
 	// Remove maintenance file, we're done.
 	$wp_filesystem->delete($maintenance_file);
 
+	// Has to be in here, rather than the Upgrader as the filter below will override and kill the process before themes get updated on major updates
+	do_action( 'upgrader_process_complete', null, array( 'action' => 'update', 'type' => 'core' ) );
+
 	// If we made it this far:
 	do_action( '_core_updated_successfully', $wp_version );