Wikipedia archive import script

This script was deleted from the core in r100128, only a year after I
wrote it (r78674). I would like it to be in version control of some
description, so that development can continue, and so that it can more
easily be found by researchers. Maybe it will live longer in this
extension.

Change-Id: Ia6f209e06d3a7a616c85a0b6d369e31a35d813f6
Merge "Wikipedia archive import script"