Bulk export (#684)

* First pass (working) collection export to zip

* Add export confirmation screen

* 👕

* Refactor

* Job for team export, move to tmp file, settings UI

* Export all collections job

* 👕

* Add specs

* Clarify UI

app/stores/CollectionsStore.js

@@ -137,6 +137,16 @@ class CollectionsStore extends BaseStore {
     }
   };
 
+  @action
+  export = async () => {
+    try {
+      await client.post('/collections.exportAll');
+      return true;
+    } catch (err) {
+      throw err;
+    }
+  };
+
   @action
   add = (collection: Collection): void => {
     this.data.set(collection.id, collection);