ext.uls.interface: clarify code

Changes to comments, naming and code to increase clarity of the code
and explain better what it does and why. No change in behavior.

Change-Id: I998fcfd620c2ee737618c3ab8f41fb6dfdd2c99a

resources/js/ext.uls.compactlinks.js

@@ -321,7 +321,9 @@
 	};
 
 	/**
-	 * Add the trigger at the bottom of the language list
+	 * Add the trigger at the bottom of the language list.
+	 *
+	 * Click handler is setup in ext.uls.interface module.
 	 */
 	CompactInterlanguageList.prototype.addTrigger = function () {
 		var trigger = document.createElement( 'button' );