Merge branch 'more-info-article-filter' into 'master'

Pass the value of cache_images to plugins in HOOK_ARTICLE_FILTER.

Adds the `$cache_images` value to the `$article['feed']` array before calling HOOK_ARTICLE_FILTER. Allows plugins to know whether images will be cached in case they want to manage them in one way or another.

See merge request !32