self-learning in engine

usage: type "testrun" in the console

Used to get a rough indication of the validity of a new evaluation features

1. Generates GAMECOUNT random start position (typically 1000 or more) using book.bin
2. Self-play GAMECOUNT games, one side has the new eval features enabled, the other side not
3. Check if the new evaluation is valid, by giving it the opposite score. (factor -1.0)
4. Repeat self-play with several positive multiplication factors, to find the optimal one

The final result is the best multiplication factor for the new evaluation feature

+ some polyglot book fixes