dep-ui.js: Use `input' events for updating deps. Factor `input_...'. Somehow I missed the `input' event on all formish widgets, which is, of course, exactly what I wanted all along. Use this for everything, rather than a mishmash of other widget-class-specific events. This means, in turn, that `input_field' and `input_radio' are almost exactly the same function now, so factor out the common machinery.
dep.js: Set up `BAD' correctly. Two bugs, which sort of cancelled each other out. * I failed to invoke `new' when I made `BAD', which meant that `BAD' actually ended up set to `undefined'. * I didn't set `DEP.val' properly if `value' wasn't passed explicitly, so, err, it ended up being `undefined', which is then erroneously considered to be equivalent to `BAD'. Fix this silliness.