Add (optional) Google Protocol Buffers support (example in Tutorial 3).

To use protobuf, run cmake as follows:
cmake -DUSE_PROTOBUF=1 ..
For this, protobuf library has to be installed on the system.

Further changes:
Clean up splitter/merger: default are N-to-1-merger and 1-to-N-splitter.
Fix bug in nanomsg message deallocation.
Setup proper buffer sizes for nanomsg/zeromq via cmake/bash script.
chmod +x for start scripts.

fairmq/FairMQDevice.cxx

@@ -315,6 +315,11 @@ void FairMQDevice::LogSocketRates()
       i = 0;
 
       for ( vector<FairMQSocket*>::iterator itr = fPayloadOutputs->begin(); itr != fPayloadOutputs->end(); itr++ ) {
+
+        // #ifdef NANOMSG
+        //   LOG(ERROR) << "OK THEN";
+        // #endif
+
         bytesOutputNew[i] = (*itr)->GetBytesTx();
         megabytesPerSecondOutput[i] = ((double) (bytesOutputNew[i] - bytesOutput[i]) / (1024. * 1024.)) / (double) timeSinceLastLog_ms * 1000.;
         bytesOutput[i] = bytesOutputNew[i];