Add Support for Proof Systems Other Than Sigma Protocols

Initial idea by @feidens : "I think it would be nice to implement another proof system (other than sigma protocols (Schnorr-like)) and see if we have interoperability in the sense "Among proof systems""
Response by @JanBobolz : "like some other proof system that can prove stuff about Pedersen-committed values? Bulletproofs? I guess that would enhance our lib, but seems very time-costly"