Many improvements; notably support for API 10+

* API 10+ means Android versions 2.3.7 and up are all supported. I'd like to bring this down to API 8, but I won't without such a phone to test it on.
* Added class to contain player information
* Renamed package to com.danylnysom.rpsduel (from com.example.rpsduel... oops!)
* Fixed typo in one of the game result messages (previously said "air tarnish gun")