Recents in create, uniform item layouts.

Show recent directories in a separate fragment, and save as serialized
versions of new DirectoryStack. Cleaner behavior around recents and
search, instead of treating them as pseudo-Documents.

More uniform item layouts between list and grid, including both date
and size information, and originating storage root in recents. Avoid
clashing directory loaders by assigning unique numbers. Promote
list/grid switching up into activity.

Change-Id: I9a93460b896067ca036d7e772eeabde31face2e1
diff --git a/res/menu/activity.xml b/res/menu/activity.xml
index a0d03b2..d57f88a 100644
--- a/res/menu/activity.xml
+++ b/res/menu/activity.xml
@@ -27,4 +27,14 @@
         android:showAsAction="always|collapseActionView"
         android:actionViewClass="android.widget.SearchView"
         android:imeOptions="actionSearch" />
+    <item
+        android:id="@+id/menu_grid"
+        android:title="@string/menu_grid"
+        android:icon="@drawable/ic_menu_grid"
+        android:showAsAction="ifRoom" />
+    <item
+        android:id="@+id/menu_list"
+        android:title="@string/menu_list"
+        android:icon="@drawable/ic_menu_list"
+        android:showAsAction="ifRoom" />
 </menu>