Zakhar Voit, 2539

~60 FPS on Nexus 5

1) Use one-dimentional arrays instead of two-dimentional ones.
2) Use drawBitmap method of canvas instead of setPixel.
3) Use caching of fields (Just draw colors if we had seen this field before).
4) Process fields in as many threads as many cores are available on device. (Not speed-up much)
very expensive since `hashcode` iterates though whole array