Make QWizard resizable in Y direction

A QWizard that contains a watermark can't be resized in Y direction. Sometimes it would be useful to be able to make such a dialog higher, even if it contains a watermark (for instance when reading a lengthy license agreement text).

Suggestion: add a new option that defines whether the wizard should be allowed to grow in Y direction, and when making it higher than the pixmap would allow, duplicate the bottom pixel line of the pixmap as often as necessary to fill up the height. This, of course, requires that the pixmap still looks good if the bottom line is duplicated several times, but that's up to the developer to make sure of.