allow admins to censor sharing drawings

Need to block an obscene sharing drawing? Now from the /sh/xxx url (if you're looking in the gallery, click on the image -- if you're looking at a social media share, should be able to click through), if you are logged in as an admin you can block the image and delete all the gallery shares:

<img src="https://www.dropbox.com/s/uk3kb5mwx55dasl/Screenshot%202014-11-24%2015.39.43.png?dl=1">

(check the checkbox and click 'Save')