gnu: Move web packages from python to python-web.

gnu: Move web packages from python to python-web.

This is in part to address <https://bugs.gnu.org/27284>.

* gnu/packages/python.scm (python-httplib2, python2-httplib2)
(python-sockjs-tornado, python2-sockjs-tornado)
(python-flask-babel, python2-flask-babel)
(python-html5lib, python2-html5lib)
(python-html5lib-0.9, python2-html5lib-0.9)
(python-html5-parser, python2-html5-parser)
(python-webencodings, python2-webencodings)
(python-openid, python2-openid, python-cssutils, python2-cssutils)
(python-cssselect, python2-cssutils)
(python-openid-cla, python2-openid-cla)
(python-openid-teams, python2-openid-teams)
(python-tornado, python2-tornado)
(python-tornado-http-auth, python-terminado, python2-terminado)
(python-webob, python2-webob, python-zope-event, python2-zope-event)
(python-zope-interface, python2-zope-interface)
(python-zope-exceptions, python2-zope-exceptions)
(python-zope-testing, python2-zope-testing)
(python-zope-testrunner, python2-zope-testrunner)
(python-zope-i18nmessageid, python2-zope-i18nmessageid)
(python-zope-schema, python2-zope-schema)
(python-zope-configuration, python2-zope-configuration)
(python-zope-proxy, python2-zope-proxy)
(python-zope-location, python2-zope-location)
(python-zope-security, python2-zope-security)
(python-zope-component, python2-zope-component)
(python-ndg-httpsclient, python2-ndg-httpsclient)
(python-websocket-client, python2-websocket-client)
(python-requests-toolbelt, python2-requests-toolbelt)
(python-rauth, python2-rauth, python-urllib3, python2-urllib3)
(awscli, python-wsgiproxy2, python2-wsgiproxy2)
(python-pastedeploy, python2-pastedeploy)
(python-webtest, python2-webtest, python-flask, python2-flask)
(python-flast-wtf, python2-flask-wtf)
(python-flask-multistatic, python2-flask-multistatic)
(python-cookies, python2-cookies)
(python-responses, python2-responses)
(python-geventhttpclient, python2-geventhttpclient)
(python-requests-oauthlib, python2-requests-oauthlib)
(python-url, python2-url, python-cachecontrol, python2-cachecontrol)
(python-betamax, python2-betamax)
(python-betamax-matchers, python2-betamax-matchers)
(python-s3transfer, python2-s3transfer)
(python-flask-restful, python-flask-basicauth)
(python-flask-sqlalchemy, python-flask-restplus)
(python-flask-restful-swagger, python-htmlmin, python2-htmlmin)
(python-flask-htmlmin, python2-flask-htmlmin)
(python-flask-login, python2-flask-login)
(python-oauth2client, python-flask-oidc)
(python-webassets, python-cssmin, python2-cssmin)
(python-elasticsearch, python2-elasticsearch)
(python-flask-script, python2-flask-script)
(python-flask-migrate, python2-flask-migrate)
(python-genshi, python2-genshi)
(python-flask-principal, python2-flask-principal)
(python-flask-httpauth, python2-flask-httpauth)
(python-uritemplate, python2-uritemplate): Move to...
* gnu/packages/python-web.scm: ... here.  New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* gnu/packages/admin.scm, gnu/packages/backup.scm,
gnu/packages/dav.scm, gnu/packages/django.scm,
gnu/packages/docker.scm, gnu/packages/ebook.scm,
gnu/packages/logging.scm, gnu/packages/mail.scm,
gnu/packages/music.scm, gnu/packages/openstack.scm,
gnu/packages/package-management.scm, gnu/packages/rdf.scm,
gnu/packages/tls.scm, gnu/packages/tor.scm,
gnu/packages/tryton.scm, gnu/packages/version-control.scm,
gnu/packages/web-browsers.scm,
gnu/packages/web.scm: Adjust accordingly.