Add decorator option for language links

Callback function to be called when a language link is prepared
Can be used for custom decoration.
Arguments:
(a) the $language - the language link jQuery object
(b) languageCode

The function can do any styling, changing properites etc on the passed link.
See examples/decorator.html for example usage.

Change-Id: I5a67654440a07cf7dfac683e22dcb5000ded0bfe

src/jquery.uls.lcd.js

@@ -246,7 +246,9 @@
 			a.className = 'autonym';
 
 			li.appendChild( a );
-
+			if( this.options.languageDecorator ) {
+				this.options.languageDecorator( $( a ), code );
+			}
 			return li;
 		},
 
@@ -386,7 +388,8 @@
 	$.fn.lcd.defaults = {
 		languages: null,
 		showRegions: ['WW', 'AM', 'EU', 'ME', 'AF', 'AS', 'PA'],
-		itemsPerColumn: 8
+		itemsPerColumn: 8,
+		languageDecorator: null
 	};
 
 	$.fn.lcd.Constructor = LanguageCategoryDisplay;