Allow saving minimax generation state
Added load saved generator state
Refactor: changed namespace style
Refactor: added missing invariant checks
Refactor: extracted GameState::new_game
Test: basic save/load
Generator runs on separate thread
Refactor: use vector instead of static array
Refactor: moved max_depth from ChoiceTree to GameTree
Test: save load a running generator

And applied some fixes
CLI while generating that allows to quit
Refactor: Added stream error checking
Save to single file in XDG_DATA_HOME/pacman_generator
Save to numbered files and load from last number