There are a lot of options so this will get really verbose, both in the code and in the documentation. But I suppose in the end a more usable widget is worth it. Thinking through this a bit more, with a `calendar` option the use of `option()` suddenly becomes messy, so let's ditch the `calendar` option idea.

@fnagel you asked this earlier but the conversation got lost in some diff somewhere, but you can take the default options values from calendar with an approach like this:

```
var calendarOptions = $.ui.calendar.prototype.options;
return $.widget( "ui.datepicker", {
	options: {
		appendTo: null,
		dateFormat: calendarOptions.dateFormat,
		eachDay: calendarOptions.eachDay,
		numberOfMonths: calendarOptions.numberOfMonths,
		...
	}
});
```