Implement source code for volunteer P2P relay servers (maybe) using DHT logic

[MavrosOplarxigos]

As discussed in the thesis the diversification of sources for retrieving serving peer records is a necessary enhancement for the scheme. Therefore, source code should be provided which when run it will allow for volunteers to start a P2P relay server themselves (which can act like DNS seed servers in Bitcoin for example).

So these volunteer maintained servers should be providing to the users with two things: serving peer records and a list of other P2P relay servers that the user can use.

Additionally, the reputation scheme mentioned in #2 can be evolved so that P2P relay servers can in turn monitor and detect users that are over-asking for serving peer records. Therefore, this protection of the network from nodes that are trying to map it can be done not only via the query frequency limits that each individual P2P relay server can set but also in a global level via this information sharing between P2P relay servers.

Furthermore, the PoW #3 logic can further be expanded into the credentials of P2P relay servers. Here, since P2P relaying is a much more privacy-critical task it would be beneficial to implement this in a way that there is an additional difficulty (i.e. computational effort) for keeping a P2P relay server certificate that works (i.e., it has PoW).