Remove jquery.i18n code that the ULS extension overrides

Instead of using the whole jquery.i18n code, use only required parts
that are not customized in MW ULS. For this define a new RL module
ext.uls.i18n.

Also refactor MW message store for jquery.i18n.

Change-Id: Idda9fe505428ade409d937314d7216ebb4232c36

lib/jquery.i18n/languages/bs.js

@@ -0,0 +1,22 @@
+/**
+ * Bosnian (bosanski) language functions
+ */
+( function ( $ ) {
+	'use strict';
+
+	$.i18n.languages.bs = $.extend( {}, $.i18n.languages['default'], {
+		convertGrammar: function ( word, form ) {
+			switch ( form ) {
+			case 'instrumental': // instrumental
+				word = 's ' + word;
+				break;
+			case 'lokativ': // locative
+				word = 'o ' + word;
+				break;
+			}
+
+			return word;
+		}
+	} );
+
+}( jQuery ) );