Change default progressbar to show off more features. Also prevent two progressbars from sharing the same default widgets.

This is a lot more contentious feature than my last one! Can we change the default widgets used by progressbar? I think that showing the count of elements processed and the estimated completion time is very informative in most of the use-cases I have for progressbar. And other than it changes the look, I don't think it would break a lot of people's code.