Remove compile time transport interface switch

- Remove the compile time check of the transport implementation.
  The transport (zeromq/nanomsg) can be chosen at run time with:
  `device.SetTransport("zeromq"); // possible values are "zeromq" and "nanomsg"`.

  For devices that use FairMQProgOptions, the transport can be configured via cmd option:
  `--transport zeromq` or `--transport nanomsg`. Default values is "zeromq".
  The device receives the configured value with:
  `device.SetTransport(config.GetValue<std::string>("transport"));`

  Old method of setting transport still works. But the NANOMSG constant is not defined.

- Remove old `fairmq/prototest` directory. It was only used as a test for protobuf.
  The protobuf part of Tutorial3 does the same (with different values).

- Fix a bug in FairMQPollerNN, where the `revents` value was not initialized.
  This caused the `poller->CheckOutput()` to trigger when it should not.

fairmq/devices/GenericMerger.h

@@ -28,9 +28,10 @@ class GenericMerger : public FairMQDevice, public MergerPolicy, public InputPoli
     virtual ~GenericMerger()
     {}
 
-    void SetTransport(FairMQTransportFactory* transport)
+    template <typename... Args>
+    void SetTransport(Args... args)
     {
-        FairMQDevice::SetTransport(transport);
+        FairMQDevice::SetTransport(std::forward<Args>(args)...);
     }
 
   protected: