chess, kcheckers and btanks added to the games spin

I have added chess, kcheckers and btanks to the games spin. I intend for that to be all of the new games for F13. I have not removed any games from those in the F12 version. Barring license or spaces issues I don't expect to remove any for F13. I expect to be able to add a few large ones back for F14 when lzma squashfs should be available. But I won't know how much extra space I'll have until the development version of squashfs-tools is available and getting it built is trickier than I had hoped due to mismatches between various lzma libraries.