FEATURE: Shared Drafts

This feature can be enabled by choosing a destination for the
`shared drafts category` site setting.

* Staff members can create shared drafts, choosing a destination
category for the topic when it is published.

* Shared Drafts can be viewed in their category, or above the
topic list for the destination category where it will end up.

* When the shared draft is ready, it can be published to the
appropriate category by clicking a button on the topic view.

* When published, Drafts change their timestamps to the current
time, and any edits to the original post are removed.

test/javascripts/helpers/create-pretender.js.es6

@@ -151,6 +151,7 @@ export default function() {
 
     this.delete('/t/:id', success);
     this.put('/t/:id/recover', success);
+    this.put('/t/:id/publish', success);
 
     this.get("/404-body", () => {
       return [200, {"Content-Type": "text/html"}, "<div class='page-not-found'>not found</div>"];