WebStyle: better HTTP return statuses 404/500

• In mod_python-like legacy publisher implementation, resolve only to callable names, otherwise return 404.

• In mod_python-like legacy publisher implementation, alert the admin via email about wrong parameters being passed only when CFG_DEVEL_SITE is True.

• In case of unexpected error, return HTTP status 500.

• Removed useless call to wsgiref.util.setup_testing_defaults.