Bug 61783: also install root pywikibot package

We only installed packages that started with 'pywikibot.'
(e.g. pywikibot.comms and pywikibot.data), but this did not
install e.g. pywikibot.page (which is the *module* page in
*package* pywikibot) as well as pywikibot/__init__.py, which
is required to import the entire package.

Change-Id: Ie2534442a8b651cf5c63c607462887b3d4a55477
Merge "Bug 61783: also install root pywikibot package"