Start the global API server
    Returns the API server thread

def api_start(working_dir, host, port, thread=True):
    """
    Start the global API server
    Returns the API server thread
    """
    api_srv = BlockstackdAPIServer( working_dir, host, port )
    log.info("Starting API server on port {}".format(port))
    if thread:
        api_srv.start()

    return api_srv