Remove pwn module and links

The pwn module has never been used, as the pwn are simply sent to
-announce and nothing else. We've kept the code and model around for
doing it on the site for years now and it's unused, so let's remove it
to cut down on maintenance cost.

pgweb/settings.py

@@ -114,7 +114,6 @@ INSTALLED_APPS = [
     'pgweb.survey',
     'pgweb.misc',
     'pgweb.featurematrix',
-	'pgweb.pwn',
 	'pgweb.search',
     'pgweb.pugs',
 ]