Fix regressions in the item displays

Fix displaying documents in the document browse and refreshing the selection
when the results have changed.

Make sure we are passing the appropriate flag to _redisplay() in GenericDisplay.

Make sure we set this._appsStale to true if there was a change in the
applications set.

Don't call _refreshCache() from the AppDisplay constructor.

Don't short-circuit the call to _refreshCache() from _redisplay() on initial load.

Rename _redisplayFull() to recreateDisplayItems() and remove adding an
actor to the actual result list in _addDisplayItem() because we redo adding the
actors to the list in _redisplayReordering() anyway to ensure that we add
them in the right order.

Based on a patch from Colin Walters.

js/ui/docDisplay.js

@@ -136,7 +136,7 @@ DocDisplay.prototype = {
             // but redisplaying right away is cool when we use Zephyr.
             // Also, we might be displaying remote documents, like Google Docs, in the future
             // which might be edited by someone else.
-            this._redisplay(false);
+            this._redisplay(GenericDisplay.RedisplayFlags.NONE);
         }));
 
         this.connect('destroy', Lang.bind(this, function (o) {