[web] Move request handling logic into cubicweb application. (closes #2200684) We improve http status handling in the process: ``application.publish`` have been renamed to ``application.handle`` to better reflect it's roles. The request object gain a status_out attribute to convey the HTTP status of the response. WSGI and etwist code have been updated. Exception gain status attribute

add_relation_type('prefered_form')

rql('SET X prefered_form Y WHERE Y canonical TRUE, X identical_to Y')
commit()

drop_attribute('EmailAddress', 'canonical')
drop_relation_definition('EmailAddress', 'identical_to', 'EmailAddress')

if 'see_also' in schema:
    sync_schema_props_perms('see_also', syncprops=False, syncrdefs=False)