[web] implement cross origin resource sharing (CORS) (closes #2491768) Partial implementation that is enough to get started but leaves out some of the advanced features like caching and non-simple methods and headers.

# -*- 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"""