verifymessage shouldn't check priv keys

Updated `VerifyMessage` to avoid checking private key and just compare the signature pubkey with the given address.

Refs #123 
This needs to serialize the public key in the same manner (compressed or uncompressed) as the recoved public key in the signature.  A single public key can result in two different Bitcoin addresses depending on if the Hash160(serialziedPubKey) is for the compressed or uncompressed serialization format.