FileDialog: ensure that arrow keys can always navigate the file list

By default the file list should be focused so that arrow keys can be
used to select a file, and so that the list has a focused appearance.
But even when the list does not have focus, the up/down arrow keys
can still navigate the list because they are not accepted by any
other controls in this dialog.

Change-Id: Ie73bb187672cce86da0e5089d16a558af92414e9
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>

src/dialogs/DefaultFileDialog.qml

@@ -54,6 +54,7 @@ AbstractFileDialog {
         if (visible) {
             view.needsWidthAdjustment = true
             view.selection.clear()
+            view.focus = true
         }
     }
 
@@ -151,6 +152,7 @@ AbstractFileDialog {
                 break
             }
         }
+        Keys.forwardTo: [view.flickableItem]
 
         SplitView {
             id: splitter