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.

examples/MQ/3-dds/ex3-dds-hosts.cfg

@@ -3,6 +3,6 @@ echo "DBG: SSH ENV Script"
 #source setup.sh
 @bash_end@
 
-sampler, username@localhost, , /tmp/, 1
-processor, username@localhost, , /tmp/, 10
-sink, username@localhost, , /tmp/, 1
+sampler, orybalch@localhost, , /tmp/, 1
+processor, orybalch@localhost, , /tmp/, 10
+sink, orybalch@localhost, , /tmp/, 1