Yeah, I was following the other helpers' convention.

I just noticed that I misread our theming docs about it, though. I thought that we should "prefer {% %} over {{ }}", but it was specific to snippets (http://docs.ckan.org/en/latest/contributing/frontend/templating.html#snippets). This was why I changed ```{{ h.url_for_static(g.site_logo) }}``` to ```{% url_for_static_or_external g.site_logo %}```.

I'm happy to move it back and remove this Jinja extensions, sticking only to ```{{ }}```, if no one knows why we have multiple ways to call them in the first place.

@seanh?