Use loadable plugins for python3 support

uwsgi cannot be linked with Python 2.x and Python 3.x at the same time
so separate Python modules must be built. As loadable modules are being
built, separate all the stuff that was compiled-in.
TODO updated

lighttpd module has been dropped. django is not there either
and for nginx, the uwsgi support has been included upstream.
Release: 1.1

incompatible changes were introduced, let us test that first