Reintroduction of `formmethod`

[xvw]

• First commit: corrects a subtle typo Formation -> Formaction in the input_attrib.
• Second commit: Even though formmethod is deprecated, the W3C specification of <input> does not accept a method attribute but rather formmethod

https://www.w3.org/TR/2011/WD-html5-20110525/the-input-element.html

I've kept the method attribute for button and input for backwards compatibility, but in an ideal world it would be removed.