refactor shelf activity on book page

- disallow moving from custom shelf to a reading status shelf with shelf_selector
- always use shelve_button for moving books from a reading status shelf
- redesign shelf information as a list of boxes

bookwyrm/templates/snippets/shelf_selector.html

@@ -1,5 +1,7 @@
 {% extends 'components/dropdown.html' %}
 {% load i18n %}
+{% load bookwyrm_tags %}
+
 {% block dropdown-trigger %}
 <span>{% trans "Move book" %}</span>
 <span class="icon icon-arrow-down" aria-hidden="true"></span>
@@ -7,6 +9,7 @@
 
 {% block dropdown-list %}
 {% for shelf in user_shelves %}
+{% if shelf.identifier|is_shelf_type:"custom" %}
 <li role="menuitem" class="dropdown-item p-0">
     <form name="shelve" action="/shelve/" method="post">
         {% csrf_token %}
@@ -16,6 +19,7 @@
         <button class="button is-fullwidth is-small shelf-option is-radiusless is-white" type="submit" {% if shelf.identifier == current.identifier %}disabled{% endif %}><span>{{ shelf.name }}</span></button>
     </form>
 </li>
+{% endif %}
 {% endfor %}
 <li class="navbar-divider" role="separator"></li>
 <li role="menuitem" class="dropdown-item p-0">