SignatureVerifier Consolidation

[samliok]

so we have a lot of different declarations of verify signature.

// api.go
type SignatureVerifier interface {
	VerifySignature(message []byte, signature []byte, publicKey []byte) error
}

// config.Go <- crypto ops interface
VerifySignature(message []byte, signature []byte, publicKey []byte) error

//msm.go
type SignatureVerifier interface {
	VerifySignature(signature []byte, message []byte, publicKey []byte) error
}

does it make sense to consolidate this into one? i think there may be a current bug in our test code since we use the same verifier to implement all 3 interfaces, even though the function signatures are different.

Originally posted by @yacovm in #427 (comment)