fix($compile): ensure that hidden input values are correct after history.back

Due to the nature of some browser's PageCache/BFCache, returning to an Angular
app sometimes causes `input[hidden]` elements to retain the last value
that was stored before the page was navigated away from previously.

This is particularly problematic if the input has an interpolated value.
E.g. `<input type="hidden" value="{{ 1 + 2 }}">` since when the browser
returns, instead of the original interpolation template, the HTML contains
the previous value `<input type="hidden" value="3">`.

This commit instructs the browser not to attempt to reinstate the previous
value when navigating back in history by setting `autocomplete="off"` on
the hidden input element element.