can override the reply Uri for in memory transport to make testing easier.  Closes GH-143
very preliminary work on test harness improvements
implementing the little bit of logic in SubscriptionsRepository
formalizing the ISubscription.LoadSubscriptions() method
handling the SubscriptionsChanged event, pulled ChannelGraph name logic into SubscriptionsRepository
fleshed out the SubscriptionRequested message handling
registered ISubscriptionRepository
building a TransportNode from a ChannelGraph
added TransportNode persistence and loading to the SubscriptionsRepository
the SubscriptionHandler message handlers are part of the FT app
cleanup of SubscriptionActivator and registration of missing subscription services