Added config options to map shibboleth attributes to user data

Added options:

- adhocracy.shibboleth.display_name.function
- adhocracy.shibboleth.locale.attribute
- adhocracy.shibboleth.register_form

Switched to JSON:

- adhocracy.shibboleth.userbadge_mapping
Enable logging to stdout for test suite (log level = INFO)
Added log output in case of invalid JSON configuration values
WIP