Add hide/show functions to wrapped-defaults
Add hide/show functions to wrapped-defaults

Summary: These are actually functions that are needed in khan-exercises,
but I'm adding them here first so that khan-exercises and perseus don't
get out of sync.

Test plan:
 - Add an interactive-graph in perseus
 - See that nothing is broken

Auditors: charlie, aria

daukantas/perseus,learningequality/perseus,alexristich/perseus,ariabuckles/perseus,ariabuckles/perseus,abe4mvp/perseus,daukantas/perseus,sachgits/perseus,chirilo/perseus,sachgits/perseus,ariabuckles/perseus,alexristich/perseus,abe4mvp/perseus,chirilo/perseus,iamchenxin/perseus,learningequality/perseus,ariabuckles/perseus,iamchenxin/perseus