Move document improvements (#927)

* Show all collections in UI

* Introduce command pattern

* Actually remove from previous collection

* Stash

* Fixes: Promises resolved outside of response lifecycle

* 💚

* 💚

* documentMover tests

* Transaction

* Perf. More in transactions

app/models/Collection.js

@@ -24,6 +24,11 @@ export default class Collection extends BaseModel {
   updatedAt: ?string;
   url: string;
 
+  @computed
+  get isPrivate(): boolean {
+    return this.private;
+  }
+
   @computed
   get isEmpty(): boolean {
     return this.documents.length === 0;