Use Codable Protocol Instead

[decanus]

To make the code more swift like, we should consider using codable types.

https://www.raywenderlich.com/382-encoding-decoding-and-serialization-in-swift-4

[apbendi]

Hey @decanus, which types are you looking to implement Codable on? The Bases58 implementation itself seems to be a couple of extensions to String and Array, while the BigInt type from the dependency already implements Codable.

[decanus]

Instead of those ugly functions in String and Array extensions it would be cool if we could replace those with Codable code. Not sure if this is feasible.