change CSV comment to say "marketplace.mozilla.org.mozilla.org Statistics" (bug 761328)

apps/stats/templates/stats/csv_header.txt

@@ -1,8 +1,12 @@
 {% if title %}
 #    {{ title }}
 {% else %}
+{% if settings.MARKETPLACE %}
+#    marketplace.mozilla.org Statistics for app {{ addon.name }}
+{% else %}
 #    addons.mozilla.org Statistics for add-on {{ addon.name }}
 {% endif %}
+{% endif %}
 #
 #    Generated {{ timestamp }}
 #    from {{ request.build_absolute_uri() }}