Deprecate SSL override configuration

No sites use this functionality, as wikimedia sites changed from
a https://secure.wikimedia.org front-end processor to using https
on the target wiki.

Also remove the 'ssl' override parameter from http.request.
The ssl param was only used with the site parameter, to support the
configuration variables, and was ignored if a uri was provided.

Change-Id: I5834ca17972e888886d15524098331cd8839f1da
Merge "Deprecate SSL override configuration"