Update v0.6.3

The main feature of this patch are AI improvements and bugfixes.

Due to sloppy code, the AI was previously making some extremely unprincipled moves, and I was able to get 5 wins in a row against "Visionary". The AI should put up a much better fight now.

Balance Changes

PEKKA: Attack 10->8

You might think this is a very big nerf, and you would be correct. PEKKA was very overpowered. The entire set of 8 units was designed, implemented, and playtested in the past 24 hours. This one slipped past playtesting.