* Revise documentation in README.md
* Inject abstract_clock in Manager
* Introduce the Slot object as a replacement for Peer
* New bullet-proof method for slot accounting
* Replace Peer with Slot for tracking connections
* Prevent duplicate outbound connection attempts
* Improved connection and bootstrap business logic
* Refactor PeerImp, PeersImp private interfaces
* Give PeersImp access to the PeerImp interface
* Handle errors retrieving endpoints from asio sockets
* Use weak_ptr to manage PeerImp lifetime
* Better handling of socket closure in PeerImp
* Improve the orderly shutdown logic of PeersImp
* Implement PeerFinder business logic.
* Support fixed peers (including DNS support).
* Add journal support to Peer and Peers.
* Refactor PeerDoor support.
* Tidy up Peers and eliminate connection functionality and timers.
* Refactor Peer interface and add journal support.
* Allow construction of incoming Peer using an existing socket.
* Remove TESTNET support.
* Allow connections from/to cluster peers without consuming slots
* Misc. cleanups.
