#226 Progress bar should display the current and maximum values

[Mikhail T.]

I'm using the ProgressBar part of BWidgets, and am
quite happy with it over all.

I find a piece of information missing, and am going to
display it in a separate label for now -- the current
value and the maximum value of the progress.

Ideally, there should be an option for these bit to be
displayed right there on the progress bar itself...