Feature summary (what you would like to be able to do and where):

Create a generator (and equivalent CLI option) that given a PagePile id, can obtain the corresponding Page objects.

Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):

There are situations when I process PagePiles without knowing the site upfront. In this case, the -url option is not enough, as the text output of PagePile does not contain Site information.

Benefits (why should this be implemented?): Much shorter to give an id rather than a full URL