As we moved most of the creation of a BufferPool to be via the
Streaming::pool() method, which uses a thread-local, it makes sense
to start cleaning up the design and make it more modern C++.
The above mentioned method would return a reference and you'd see
loads of places use `auto &pool =` which is less than ideal.
As the number of places where we actually instantiate a BufferPool
goes down, the usage of some sort of smart pointer makes more sense.
This now makes all APIs use BufferPool be wrapped in a shared_ptr.
THe builder now allows you to create a message with the
serviceId, the messageId and the requestId pre-set.
This benefits code that just takes the output from the
builder and calls 'send' on it immediately saving several
lines of code.
This is an overload of message() specifically meant to build
replies to incoming messages.
The behaviour changed here is that incoming messages with
headers other than "RequestId" now get copied to the outgoing
message by default.
tomFlowee
TomZ