Android: Show transition animations on game start / end.

[sigmabeta]

This gives the user something to look at while their game is being loaded, and doesn't affect load-times in any tangible way.

The transition back to the grid is slowed down a little bit (the attached video exacerbates this because duh, writing a video to disk while writing a screenshot) and is also a little bit glitchy. I'm working on fixing that, but it will require deeper changes (probably a non-Picasso image library.)

I think it looks pretty cool already, but it'll look even cooler once the save/load flow is in.

I'll upload some gfycats of what it looks like when those are done processing.

[sigmabeta]

Here's the game-start animation:
http://gfycat.com/UntimelyAgedBactrian

If anyone knows how to embed that straight into a GH comment, that'd be great.

[sigmabeta]

And here's the game-end animation:
http://gfycat.com/ForkedJubilantDingo

The grid doesn't load the new image fast enough at the end, so you see the old image temporarily. It gets replaced after approx a quarter of a second, but I stopped recording too soon. A faster image loading library might fix this.