implement saving of .sgf files with stone and player setup nodes (#295)
implement saving of .sgf files with stone and player setup nodes (#295)

adding stone setup and player setup handling to SyncGTPEngineCommand
is obviously also important for playing against the computer after
changing board positions, and after the app is relaunched and has to
set up Fuego to match the game that was unarchived via NSCoding.

herzbube/littlego,herzbube/littlego,herzbube/littlego,herzbube/littlego,herzbube/littlego