Fix reset button in demo

[bochoven]

And consolidate button checks in one handler

[zmip]

Sorry, I wrecked this pr. But what is button type menu?

return type in {button:0, reset:0, submit:0, menu:0};

https://www.w3.org/wiki/HTML/Elements/button

[bochoven]

See https://html.spec.whatwg.org/multipage/forms.html#the-button-element and https://developer.mozilla.org/en/docs/Web/HTML/Element/button