Add signWithSHA128:error: and verifySignatureWithSHA128:message:

Needed to sign some data using SHA1 hashing, but it was not implemented :(
I have added two methods to sign and verify on MIHRSAPrivateKey and MIHRSAPublicKey which uses SHA1 hashing.

    - (BOOL)verifySignatureWithSHA128:(NSData *)signature message:(NSData *)message;
    - (NSData *)signWithSHA128:(NSData *)message error:(NSError **)error;