Allow disabling transfer rate logging per input/output (optional, default is on).

This commit introduces new property to FairMQDevice to control whether rateLogger thread should print rates for a given input/output.
Per default logging is enabled, so existing code works as before and does not need to be updated.
To turn off logging for an initialized input/output, set the `LogInputRate`/`LogOutputRate` property to `0`.

Example:
``` c++
splitter.ChangeState(FairMQSplitter::INIT);
// turn off rate logging for input 1 and output 4
splitter.SetProperty(FairMQSplitter::LogInputRate, 0, 1);
splitter.SetProperty(FairMQSplitter::LogOutputRate, 0, 4);
```