With this commit we're now using the naming "bootstrap node" everywhere
as opposed to the more fuzzy notion of "seed node" (which was originally
borrowed from Bitcoin Core, but doesn't really describe what we're up to
very well.
As it turns out, Kademlia also uses the terminology "bootstrap node" [1], so
we're in good company with this change.
[1]: https://en.wikipedia.org/wiki/Kademlia#Joining_the_network
