Add bundles for organizing bookmarks (#1097)

* add bundle model and query logic

* cleanup tests

* add basic form

* add success message

* Add form tests

* Add bundle list view

* fix edit view

* Add remove button

* Add basic preview logic

* Make pagination use absolute URLs

* Hide bookmark edits when rendering preview

* Render bookmark list in preview

* Reorder bundles

* Show bundles in bookmark view

* Make bookmark search respect selected bundle

* UI tweaks

* Fix bookmark scope

* Improve bundle preview

* Skip preview if form is submitted

* Show correct preview after invalid form submission

* Add option to hide bundles

* Merge new migrations

* Add tests for bundle menu

* Improve check for preview being removed

bookmarks/templates/shared/messages.html

@@ -0,0 +1,9 @@
+{% if messages %}
+  <div class="message-list">
+    {% for message in messages %}
+      <div class="toast toast-{{ message.tags }}" role="alert">
+        {{ message }}
+      </div>
+    {% endfor %}
+  </div>
+{% endif %}