Update multi-part features (nanomsg) and various fixes

- Implement nanomsg multipart with MessagePack.
 - Use the MessagePack from FairSoft and handle not found case.
 - Update splitter, merger and proxy devices to handle multi-part.
 - Let FairMQParts.At() return pointer reference (can be used for moving).
 - Add missing const specifier in the message interface.
 - Add transmit kernel size setting to channels (ZMQ_SNDBUF).
 - Remove FairMQBuffer device.
 - Remove old multi-part methods from Tutorial3 example (to be replaced with Parts API).
 - Make callback mandatory for newMsg(data, size, callback).
 - Add missing <vector> include in FairMQSocket.

fairmq/FairMQDevice.h

@@ -150,7 +150,7 @@ class FairMQDevice : public FairMQStateMachine, public FairMQConfigurable
     /// @param ffn optional callback, called when the message is transfered (and can be deleted)
     /// @param hint optional helper pointer that can be used in the callback
     /// @return pointer to FairMQMessage
-    inline FairMQMessage* NewMessage(void* data, int size, fairmq_free_fn* ffn = NULL, void* hint = NULL) const
+    inline FairMQMessage* NewMessage(void* data, int size, fairmq_free_fn* ffn, void* hint = NULL) const
     {
         return fTransportFactory->CreateMessage(data, size, ffn, hint);
     }