validation widget parameters / api documentation

[bill]

The valiation widgets deal with parameters in a strange way, overriding mixInProperties() rather than doing any necessary processing in postMixInProperties(). This makes the code hard to understand, overly wordy, and more importantly the API tool won't pick up the documentation for each widget parameter.

Need to use standard way to declare parameters (like all the other widgets)

[Adam Peller]

addressed by new widget code