Secret sharing

The implemented schemes are prototypes and should not be used in production. They are used to assist in demonstrating threshold signatures (in other repos).

1. Shamir secret sharing (Requires trusted third party)
2. Pedersen verifiable secret sharing (Requires trusted third party)
3. Pedersen decentralized verifiable secret sharing (Does not require a trusted party)

Pending:

1. More tests
2. Model Pedersen DVSS as state machine