Make the CA work also with ECC

[MavrosOplarxigos]

By having a CA that can also work with ECC we are opting the user to choose between the existing solution (of using RSA certificates) vs a more efficient solution which is computationally less intensive and still provides for a sufficient degree of security.

In turn, we would have to consider if a user that prefers efficiency over privacy-enhancement would also have to provide PoW #3 in its certificates. Also should ECC certificates be accepted by other users if that PoW doesn't exist in such users' certificates? Should an efficiency oriented portion of the user population use the same P2P relay servers then?