Fix Bug 39686 - Cancel button in settings should go to the previous context

* Add an onClose option for language settings
* Add a close method to language settings and display settings
* some documentation and cleanup

Change-Id: I3040e0740bd8a9f9f7d3ad508a3003415a24e7a9

resources/js/ext.uls.init.js

@@ -110,6 +110,10 @@
 			uls.$menu.find( "div#settings-block" ).append( $displaySettings );
 			var position = uls.position();
 			$displaySettings.languagesettings( {
+				defaultModule: $.fn.languagesettings.modules['display'],
+				onClose: function () {
+					uls.show();
+				},
 				top: position.top,
 				left: position.left
 			} );