terminate_zmq() not called on exit - can leave sockets hanging

[avinxshKD]

was looking through the ZMQ code in concore.py and noticed that terminate_zmq() exists but nothing calls it automatically when the script ends. You have to remember to call it yourself.

Some of the example files do call it manually (like in 0mq/firstNode.py) but if someone forgets or the program crashes, the sockets just stay open. Can cause "address already in use" errors when you try to restart.

Simple fix would be registering it with atexit:

import atexit
atexit.register(terminate_zmq)

[avinxshKD]

Ready to go, Just let me know what do you think @pradeeban ....thanks