Define the pubkey and checksum format in a class
Following #301 (closed).
In the case we want to continue using the
<pubkey>:<checksum> checksum system, and not using #341
base58.b58(de|en)code_check(), defining in DuniterPy the public key and the checksum format in a class would make things clear.
In this class we could clearly define
checksum variables and methods around them.