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/zeromq/FairMQTransportFactoryZMQ.cxx

@@ -5,11 +5,15 @@
  * @author: A. Rybalchenko
  */
 
+#include "zmq.h"
+
 #include "FairMQTransportFactoryZMQ.h"
 
 FairMQTransportFactoryZMQ::FairMQTransportFactoryZMQ()
 {
-  LOG(INFO) << "Using ZeroMQ library";
+  int major, minor, patch;
+  zmq_version (&major, &minor, &patch);
+  LOG(INFO) << "Using ZeroMQ library, version: " << major << "." << minor << "." << patch;
 }
 
 FairMQMessage* FairMQTransportFactoryZMQ::CreateMessage()