Single player mode initial version

[klieret]

OK this turned into way too many changes. We should call about this.

Biggest change is to have a new tournament class which takes some responsibilities from the game class. The game class should now only run the game and parse outputs, but no longer keep track of rounds etc. (that simply didn't work with the "single player" mode, because we can't just auto-increment rounds when we e.g., just want to evaluate a player against all its previous versions).

However, removing the round logic from the game class meant that we had to refactor how we determine winners (because that was based on the round log files as files). So instead now we get the output of the logs just as return values and determine_winner takes the as a string input.