Add coroutine for concurrency
From https://discuss.tryton.org/t/thread-less-long-polling/960
review53501002 adds a coroutine option to use gevent instead of multi-threaded server.
From https://discuss.tryton.org/t/thread-less-long-polling/960
review53501002 adds a coroutine option to use gevent instead of multi-threaded server.