This commit integrates BitFury's current routing functionality into lnd. The
primary ochestration point for the routing sub-system in the routingMgr. The
routingMgr manages all persistent and volatile state related to routing within
the network.
Newly opened channels, either when the initiator or responder are inserted into
the routing table once the channel is fully open. Once new links are inserted
the routingMgr can then perform path selection in order to locate an "optimal"
path to a target destination.
