Add the ability to configure hash algorithm for BitcoinLike currencies

[pollastri-pierre]

Currently we only use sha256 as the hashing algorithm for blockchain protocols based on Bitcoin. Some currencies are using different hashing algorithm and we need to abstract this.

The most flexible solution will be to abstract hashing for every single case we need to hash:

• The hash function used to compute transaction hash
• The hash function used to derive public keys
• Hash function to compute challenge to sign
• ...