More exception safety in incomingHandshakeH
Default values, more detailed client pool output
Small refactorings
Refactor workerWatcher: O(n^2) -> O(n)

Previously, each iteration of the worker watcher cleaned up the entire
DB instead of just looking up its own entry, which lead to O(#workers^2)
complexity.
Refactor handshaking
Refactor bootstrap server loop
Fix 'too many USNs' problem

Having restarts during the initial launch of the bootstrap server's node
pool seemed to be pretty bad. I'm not sure what the exact reason for
this behaviour is, but I would assume that nodes don't time out fast
enough in this critical stage of the network creation, leaving orphan
connections open that block new connections from being formed. When the
timeouts finally kick in, everything dies.
Merge 'wrong USN count' branch into develop