improve group page layout

- move 'Add list' button down to the group lists
- move member search box underneath members heading
- note about members being able to create lists is now under lists heading

bookwyrm/templates/groups/find_users.html

@@ -2,8 +2,5 @@
 {% load i18n %}
 
 {% block searchresults %}
-    <h2 class="title is-5">
-        {% trans "Add new members!" %}
-    </h2>
     {% include 'groups/suggested_users.html' with suggested_users=suggested_users %}
 {% endblock %}