Switched back to the native navigation drawer, re-using the layout created for SlidimgMenu though. As such, we now also have a proper drawer indicator (and a basic logo for it to work). The nav drawer is shown in all of the top-level activities.

The user can now load more results when searching for items (either from the search activity or from the category list). Shows a nice loading animation while downloading more results.

Generic overflow button removed in all activities. The crash when pressing the back button while loading search results has been fixed. The drawer tutorial now properly ties into the 'first launch' code and shows after the initial download dialog.