Add support for plain vanilla transaction signing.

[matiwinnetou]

Transaction deserialisation between various Cardano clients can be tricky so if one client prepares a transaction and CCL deserialises it and we sign it, it is not guaranteed to work.

In fact we recently stumbled exactly this case with Hydra, where new Hydra 0.13.x protocol prepares transactions which are not sign to be signed by the client. Signing them with CCL using Transaction.deserialisation and TxSigner fails.

Provided ability in quick-tx and outside of quick-tx to simply sign transactions based on bytes only, without having to deserialise, sign and then serialise again the whole transaction.