Introduce new redirect method - HTML

[judgej]

The Authorize.Net DPM gateway requires a redirect in the notify handler to handle data entry errors correctly. It does not use POST or GET redirect, but a HTML redirect. The method for doing that is here:

https://github.com/thephpleague/omnipay-authorizenet/blob/master/src/Message/SIMCompleteAuthorizeResponse.php#L93

I would like to suggest that these three redirect methods are pulled together in one place. For now, the HTML redirect method could be moved from AuthorizeNet to OmniPay common. How it would be handled in V3, I don't know.

The HTML redirect method happens to be the only one that will redirect a browser from a HTTPS to a HTTP page without a security warning, so it may be useful for other gateways.

[delatbabel]

VTPayment (China) does the same.