Added track by to optmize ng-repeat

- Added attr-id to facilitate testing e2e

Author: luancurti

src/paging.js

@@ -94,15 +94,16 @@ angular.module('bw.paging', []).directive('paging', function () {
                 '<li ' +
                     'title="{{Item.title}}" ' +
                     'data-ng-class="Item.liClass" ' +
-                    'data-ng-repeat="Item in List"> ' +
-                        '<a ' + 
+                    'data-ng-repeat="Item in List track by $index"> ' +
+                        '<a ' +
                             (attrs.pgHref ? 'data-ng-href="{{Item.pgHref}}" ' : 'href ') +
                             'data-ng-class="Item.aClass" ' +
                             'data-ng-click="Item.action()" ' +
-                            'data-ng-bind="Item.value">'+ 
+                            'data-ng-bind="Item.value">'+
+                            'ng-attr-id="$first || $last ? $index : undefined"'
                         '</a> ' +
                 '</li>' +
-            '</ul>' 
+            '</ul>'
     }