Added migration for previews on_delete=SET_NULL changes
Homepage news items can now be any page type
Added feed_image and listing_intro fields to ShowStandardPage
Removed some accidentally committed code
Updated wagtail
Swapped pyelasticsearch/elasticutils for elasticsearch-py
Updated wagtail again fixing a search bug
Changed wagtail version back to what it was and just cherry-picked fix to embeds
Use latest version of wagtail fep branch (oops)
Revert "Swapped pyelasticsearch/elasticutils for elasticsearch-py"

This reverts commit cb017f7b2dc76fd1023f67b59079d5ec8a65ba19.
Use specific page type when displaying news items on the homepage