v0.3.6

Fixes from a fifth code audit: Plex auto-play, black-bar cropping,
keep-awake and the installer.

Fixed

• Plex auto-play: when one episode failed to open, the following ones
  failed too. Now only that one is skipped; if the server can't be
  reached, playback stops at once with "Can't reach the Plex server"
  instead of trying every remaining episode.
• Crop black bars no longer mistakes a dark sky or a shadow on one side
  for a bar; after "No black bars found" pressing again retries.
• Episodes started from Recently played continue in episode order.
• The Plex sign-in dialog notices when the code expires.
• B closes Advanced statistics, which no longer stays over the
  library after stopping.
• The Subtitles menu shows a downloaded subtitle right away.
• Keep-awake is sturdier: it can't get stuck or use CPU if the system
  session changes, and the info panel says if it stopped.
• The installer keeps the current version installed until the new one is
  in, and adds the shortcut to every Steam account on the device.

Changed

• Paused playback uses less battery (no periodic redraws).
• Changing the sort order of a Plex library is instant.