I18n version of gph-site

[enigmathix]

This is the i18n version of gph-site, so that a puzzle hunt can easily be made in any language by creating a translation file and changing the LANGUAGE_CODE setting. The updated README explains the process. The code was tested with a real world French puzzle hunt. The code changes fall into 3 categories:

• python changes: wrap all user-facing texts in _(...) (_ is the usual alias for the gettext function from django.utils.translation)
• template changes: load i18n and wrap all texts in {% translate ... %} or {% blocktranslate ... %}...{% endblocktranslate %}
• javascript changes: the gettext function from the JavaScriptCatalog view is used, similarly to python

A few more code changes were necessary:

• date/time formats have to use the django (php) style instead of python. they are no longer hard-coded but localized under gph/formats/<lang>/formats.py. django uses this for the admin interface as well.
• strings containing unicode characters (e.g. unicode apostrophe) have to be explicitly defined as such in the python code (u'...')
• metadata in puzzles/models.py and puzzles/__init__.py include verbose table and field names (including plurals) so they can be translated for the admin interface
• __doc__ field in shortcuts now dynamically filled in so that it can be translated (this was hacky anyway)
• hint status code value displayed in discord now shown as full text (more useful anyway)
• svg files (answers and hints) now use a text tag so they can easily be translated
• to improve caching performance (especially for javascript but it improves caching across the site), django.middleware.http.ConditionalGetMiddleware was included to support Etags
• a French translation is included in the branch in locale/fr_FR/LC_MESSAGES/django.po and locale/fr_FR/LC_MESSAGES/djangojs.po
• not done: impersonation logs category in the admin interface is shown in English, there's apparently no way to localize this

If you merge this, please squash the commits.

[cesium12]

Thanks! I'd like to accept this as it seems useful for other teams who may want to run non-English hunts. However, these changes are extensive; we'll do our best to keep strings translated when we make changes or add features, but we won't have the resources to thoroughly verify that we haven't missed or broken anything. I'm not going to put you on the hook for maintenance, but if you'd like, you could add yourself to the README as a point of contact for any teams who may need i18n help.

[enigmathix]

I added my address in the README file.

I'd be glad to help with possible issues but the worst that could happen is if new strings are added and the existing i18n syntax is not followed (e.g. _(...) in python and {% translate ... %} in templates), then those would be harder to track down. Regardless, it won't break anything though, the English text would just appear on the site.

Thanks.

[enigmathix]

I think I addressed all the changes mentioned above. Let me know if I missed any.

[cesium12]

Thank you!