Feat/monitor poll

[lp35]

This MR improve monitor_t class by addressing #381 and #109.

This lead to better application design and allows the same thread to do both monitoring and retrieving messages from the monitored socket, thus avoiding clunky code with threads joining everywhere.

[lp35]

Additional information:

• get_event() is not compatible with zmq version < 4
• if legacy compatibility with 3.x can be dropped for check_event(), the new get_event() method can be used to avoid duplicated code in check_event()

[sigiesec]

Any update on this? Is there anything you need to address the comments? Sorry I didn't get back until now, but from reading your responses I assumed that most things are clear and undisputed.

[lp35]

Hi,

Thanks for pinging back. I'm struggling to find some time to fix those issues. I will try to do my best in the next couple of weeks.

Cheers