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/nanomsg/FairMQSocketNN.cxx

@@ -8,6 +8,7 @@
 #include <sstream>
 
 #include "FairMQSocketNN.h"
+#include "FairMQMessageNN.h"
 #include "FairMQLogger.h"
 
 FairMQSocketNN::FairMQSocketNN(const string& type, int num) :
@@ -62,6 +63,7 @@ size_t FairMQSocketNN::Send(FairMQMessage* msg)
   } else {
     fBytesTx += rc;
     ++fMessagesTx;
+    static_cast<FairMQMessageNN*>(msg)->fReceiving = false;
   }
 
   return rc;
@@ -77,6 +79,7 @@ size_t FairMQSocketNN::Receive(FairMQMessage* msg)
     fBytesRx += rc;
     ++fMessagesRx;
     msg->SetMessage(ptr, rc);
+    static_cast<FairMQMessageNN*>(msg)->fReceiving = true;
   }
 
   return rc;