0.7.0-1

New: Savestates

This adds the ability to easy restore the game from within the UI.

The changes was requested by @Sematre in #10 and should make playing casual or long games more fun. You can also use this to swap the game mode (changing the bot difficulty mid game or enabling/disabling the bot at all).

Be aware that quitting a game will discard all of your undo steps. Continuing the game will only allow you to undo to the point you continued the game from.

There were also some slight message changes (some engine error messages didn't fit in the bottom line).