Implement automatic, and more secure keypair generation, loading and storing.

[vkoskiv]

Right now the keypair is manually generated with openssl ecparam -genkey -name secp256k1 -noout -out private.pem openssl ec -in private.pem -pubout -out public.pem

And the path to these is provided in State.swift:71 self.clientWallet = Wallet(withKeyPath: "/path/to/your/keys/")

Preferrably we'd generate these if need be, and store them in a better place. This works for now, however, since this implementation is purely meant to be used by interested developers, not end-users.