Added fsmonitor to .gitignore
Use XDG_CONFIG_HOME for configuration directory.
Sort keys when writing settings.
Centre about box on main window, not the screen.
Handle case when file is not a regular file or directory.
Tweaked AUI flags, removed frozen_or_hidden_window (not needed any more).
Added utility function pid_exists()
Check pid specified in instance file is valid before trying to connect.
Moved instance file to temp dir.