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 test starts to become long to run and using the one main.cpp
hack we had removes our ability to select one test to run, so lets
go back to one executable per class.
This supplies a push notification on txid becoming known to the Hub.
Additionally this changes its close relative the AddressMonitorService
to use a different tag for the transaction data and the
double-spend-proof data so as to make it obvious which one is being
sent.
tomFlowee
TomZ