Ignore "Auto-start QC and exit QCLauncher" when holding shift-key

[PredatH0r]

Instead of having to delete the config file, please allow a user to enter the GUI mode again when he holds the shift key while QClauncher starts, basically like a shift+double click on the desktop shortcut

[syncore]

It's currently possible to bring up the UI by starting qclauncher with the -show argument instead of having to delete the configuration file. I could probably add support for holding down the SHIFT key, but I am concerned that this will block the start-up process for at least 2 seconds. I can investigate this later this week