[READY] Prevent duplicate environment clones

Upon clicking CLONE after selecting an already cloned environment, a warning appears telling the user:

![NO](http://cdn.alltheragefaces.com/img/faces/svg/angry-no.svg)

The user is however presented with a link through to that environment so they can still see what it looks like.

![YAY](http://sameffect.com/wp-content/uploads/2013/06/happy-meme.png)