[O] [NEW EXPORTER] [BUG] HTML_CONTAINER_CLASS property ignored

[Rick Frankel]

Nicolas-

The new HTML exporter does not actually use the value of the
:HTML_CONTAINER_CLASS: property. The old exporter saved the value off
into the property :html-container-class on the headline (with
`org-export-remember-html-container-classes'), the new exporter
references the `:html-container-class' property on the headline, but i
see no way to set it.

My guess is that on ox-html.el:1917 (the only reference to 
:html-container-class)
   
   (extra-class (org-element-property :html-container-class headline))

should be

   (extra-class (org-element-property :HTML_CONTAINER_CLASS headline))

Does this seem the correct fix to you?

rick