Mutitheard downloading waveforms

[xumi1993]

Is your feature request related to a problem? Please describe.
Mutitheard downloading waveforms.

Describe the solution you'd like

• Define a function like star_download
• Open a ThreadPool and throw arguments of star_download into the ThreadPool.
• Following mass_download in obspy

def star_download_mseed(args):
    """
    Star maps the arguments to the
    utils.download_and_split_mseed_bulk() function.

    :param args: The arguments to be passed.
    """
    try:
        ret_val = utils.download_and_split_mseed_bulk(
            *args, logger=self.logger)
    except utils.ERRORS as e:
        msg = ("Client '%s' - " % args[1]) + str(e)
        if "no data available" in msg.lower():
            self.logger.info(msg.split("Detailed response")[0].strip())
        else:
            self.logger.error(msg)
        return []
    return ret_val

pool = ThreadPool(min(threads_per_client, len(chunks)))

pool.map(
      star_download_mseed,
      [(self.client, self.client_name, chunk) for chunk in chunks])
pool.close()