[skeleton,pyramid] Move pyramid app definition in cubicweb.pyramid module The application definition is actually not specific to the final "cube" being bootstrapped from skeleton. This patch thus move the pyramid application function into cubicweb.pyramid module and let cubicweb register the "paste.app_factory" entry point (instead of the bootstrapped cube). Useless call to `config.scan` is dropped along the way.

# -*- coding: utf-8 -*-
# copyright %(year)s %(author)s, all rights reserved.
# contact %(author-web-site)s -- mailto:%(author-email)s
#
%(long-license)s
"""%(distname)s specific hooks and operations"""