fix(form): prevent page reload when form destroyed

this fix ensures that we prevent the default action on form submission
(full page reload) even in cases when the form is being destroyed as
a result of the submit event handler (e.g. when route change is
triggered).

The fix is more complicated than I'd like it to be mainly because
we need to ensure that we don't create circular references between
js closures and dom elements via DOM event handlers that would then
result in a memory leak.

Also the differences between IE8, IE9 and normal browsers make testing
this ugly.

Closes #1238