Volley images

 Add support for using Volley to load remote images instead of UIL

    1. Gives us Caching
    2. Load images at full resolution, rather than hardcode them. This is
       done by trying to fetch an image at highest width possible for the
       particular view. If it 500s, we assume that the image is smaller
       than the requested width and just request the full size image
    3. Created a MediaWikiImageView, to which you can pass a Media object
       and it will display it. Takes care of sizing, etc. Optionally you
       can also specify a view to use as the 'loading' view.

    TODO:
    Loading from content:// URIs still use UIL. Need to write a Volley
    HTTP Stack that can fake responses for content:// URIs.