Dethread and Context Instance

Get current zmq Context instance instead of new context.

Dethread the add peer method
Refactor connection object

Move socket and stream connection to initializer.
Dethread methods

Close socket method call

We need to close up the socket and stream when removing the active peer.
Removed check_port method
Purge create_zmq_socket unused method
Remove DarkMarket sample photos
Merge pull request #769 from hoffmabc/experimental-zmq-fixes

ZeroMQ refactor of socket creation