Mac GUI: shutdownLogging should always get called on termination
Mac GUI: dont let users attempt to relaunch if gemrb is already running
Mac GUI: let the current run loop iteration finish

before attempting to launch gemrb. fixes the launch button being "stuck"
also much more appropriate (backtrace will be cleaner/shorter etc)
Mac GUI: add pereference for terminating when game window closes

currently disabled since GemRB will crash horribly if it is relaunched due to things like plugins not being unloaded/reinitialized