FairMQ: Extend Multipart and messaging API

- Extend the multipart API to allow sending vectors of messages or helper
   thin wrapper FairMQParts. See example in examples/MQ/8-multipart.
 - NewMessage() can be used in devices instead of
   fTransportFactory->CreateMessage().
   Possible arguments remain unchanged (no args, size or data+size).
 - Send()/Receive() methods can be used in devices instead of
   fChannels.at("chan").at(i).Send()/Receive():
   Send(msg, "chan", i = 0), Receive(msg, "chan", i = 0).
 - Use the new methods in MQ examples and tests.
 - No breaking changes, but FAIRMQ_INTERFACE_VERSION is incremented to 3
   to allow to check for new methods.

fairmq/run/startBenchmark.sh.in

@@ -24,6 +24,8 @@ echo "Usage: startBenchmark [message size=1000000] [number of messages=0]"
 
 SAMPLER="bsampler"
 SAMPLER+=" --id bsampler1"
+#SAMPLER+=" --io-threads 2"
+#SAMPLER+=" --transport nanomsg"
 SAMPLER+=" --msg-size $msgSize"
 SAMPLER+=" --num-msgs $numMsgs"
 SAMPLER+=" --config-json-file @CMAKE_BINARY_DIR@/bin/config/benchmark.json"
@@ -31,6 +33,8 @@ xterm -geometry 80x23+0+0 -hold -e taskset 0x1 @CMAKE_BINARY_DIR@/bin/$SAMPLER &
 
 SINK="sink"
 SINK+=" --id sink1"
+#SINK+=" --io-threads 2"
+#SINK+=" --transport nanomsg"
 SINK+=" --num-msgs $numMsgs"
 SINK+=" --config-json-file @CMAKE_BINARY_DIR@/bin/config/benchmark.json"
 xterm -geometry 80x23+500+0 -hold -e taskset 0x2 @CMAKE_BINARY_DIR@/bin/$SINK &