remove unnecessary #import of GtpCommand.h
LoadGameCommand no longer uses callbacks to run GTP commands
add enum to SyncGTPEngineCommand for better readability
improve readability and error handling in PlayMoveCommand
change default for GtpCommand execution from asynchronous to synchronous
NewGameCommand now executes all of its GTP commands synchronously
rename GtpCommand convenience constructor
add more logging, improve existing logging
create constant for icon resource string accidentally left in the code
rename several classes
ApplicationStateManager now safeguards that restoreApplicationState is invoked under proper conditions
rename commands related to backup .sgf file

the rename is made to unambiguously indicate that the commands are concerned with
the game that is represented by an .sgf file, not with the game that is represented as
an NSCoding archive file
refactor principal method in ComputerPlayMoveCommand into smaller pieces
fix array dimensions in GoUtilities' verticesForHandicap:boardSize:
display build date/time in About screen (closes #161)
user can no longer place stone on behalf of computer player (fixes #160)
board size is now correct after UI is rotated while board is zoomed (fixes #162)