Add aaguid as a member of Assertion response to distinguish authenticator

[kj84park]

What is this PR for?

Overview or reasons

Regarding #12

Tasks

• Add aaguid as a member of VerifyCredentialResult. (When authentication is success)
• Add aaguid as a member of ASSERTION_SIGNATURE_VERIFICATION_FAIL exception response.
• Update API Guide.

Result

Success

public class VerifyCredentialResult implements ServerAPIResult {
    private ServerResponse serverResponse;
    private String aaguid;
    private String userId;
    private boolean userVerified;
    private boolean userPresent;
}

ASSERTION_SIGNATURE_VERIFICATION_FAIL Exception

... "body":{"serverResponse":{"description":"AAGUId: adce0002-35bc-c60a-648b-0b25f1f05503","internalError":"ASSERTION_SIGNATURE_VERIFICATION_FAIL","internalErrorCode":56,"internalErrorCodeDescription":null}}