OpenPixels 1.0.5 for Android

- Tiles are processed side by side (up to half the cores, at most four,
  limited by free memory); the result is identical to one at a time.
- Stop takes effect within a model step, and the button changes to
  Stopping... at once.
- Progress moves inside each tile, and a time left appears once a job has
  run for ten seconds.
- The output is capped at 16 megapixels on a phone, so a 12 MP photo at 2x
  needs 70 tiles instead of 165.
- The photo crosses to the engine in 2 MB pieces instead of one JSON array,
  which kept large photos from being killed for memory.