175078001-add-image-question-to-has-embeddables
175078001-add-image-question-to-has-embeddables

When we did the has_embeddables work, we failed to include
images questions as an embeddable association.

See https://github.com/concord-consortium/rigse/pull/861/files

[#/175078001]
https://www.pivotaltracker.com/story/show/175078001

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