MessageProcessor: Use raw zmq socket

makes transition to CurveZMQ easier

removes some cron and timeout functionality, will be re-added when required
In fact Marko pointed out the other day that market offers only have to process when something new is added to the order book. Market offers also have an expiration date, so potentially they would only have to run once per day for that.

Similarly, payment plans only have to run once per day -- at least for conventional payment plans, most of them only trigger once per week or per month, with the daily trigger only used for expiration as well.

As for smart contracts, how often should they run? Once per minute? Once per hour? Once per day? It all depends on how they are being used. Perhaps the frequency should be in the server contract and then the users can decide which servers best fit their needs. Having them every 30 seconds was useful for testing but may be overkill for production.