Made control scheme more robust

When I first downloaded this application, I found the control scheme somewhat frustrating and difficult to use, and decided to try to add additional movement options.  I was impressed with the simplicity of the code base, which made adding these changes quite simple.

The original control scheme is completely unaffected; this is purely an additional way to move the character.  Instead of only allowing movement by dragging, now the player can tap in an empty square that the character has access to.  Any invalid square, when tapped, does nothing.  If the player is adjacent to a diamond, then tapping the diamond moves it if there's nothing on the opposite side of it.

I also reduced the minSDKVersion because I have an Android 2.1 device and was curious if there were any issues for it.  The application seems to run perfectly fine on 2.1, and the version of this on the market seems to also be 2.1-compatible.

There were also a few autogenerated files that changed when I imported the project into Eclipse.  I don't know what the common practice is for files like this, as I'm new to contributing to open-source projects.  I would have told Git to ignore them if I had thought longer about the first commit.

If you are still actively maintaining this repo, I hope you consider merging this minor change into the main branch, so it can be updated on F-Droid and the Android market.  I think it makes the game more precise and fun to play, and that players can benefit from it.