MessageProcessor: Use raw zmq socket

makes transition to CurveZMQ easier

removes some cron and timeout functionality, will be re-added when required


In general poll is used for waiting for more events. In this case we want to wait for incoming data or for a specific moment. We already using poll [here](https://github.com/Open-Transactions/opentxs/blob/develop/src/ext/OTSocket.cpp#L280) to combine input events and time event (timeout). My suggestion is to  cover another time event (cron timer) into similar loop.

Simply solution is to decrease timeout in OTSocket::Receive to 100ms (so cron can be run 10 times per second).