Qopen windows multiprocessing support

[trichter]

Starting with v2.4 Qopen will also run on Windows (besides Linux and OSX).

Though, multiprocessing is not yet working, because of:

 RuntimeError:
        An attempt has been made to start a new process before the
        current process has finished its bootstrapping phase.
        This probably means that you are not using fork to start your
        child processes and you have forgotten to use the proper idiom
        in the main module:
            if __name__ == '__main__':
                freeze_support()
                ...
        The "freeze_support()" line can be omitted if the program
        is not going to be frozen to produce an executable

I think the scripts are already all started via this idiom, but maybe some imports must be moved into functions?

I will not work further into this direction, but if anybody wants to do this, I am glad to help.