Added thumbnails

Merge remote-tracking branch 'cover/thumbnails' into development

# Conflicts:
#	cps/admin.py
#	cps/templates/layout.html
#	cps/ub.py
#	cps/web.py
Update join for sqlalchemy 1.4

cps/templates/author.html

@@ -37,7 +37,7 @@
       <div class="cover">
         <a href="{{ url_for('web.show_book', book_id=entry.id) }}">
             <span class="img">
-              <img src="{{ url_for('web.get_cover', book_id=entry.id) }}" />
+              {{ book_cover_image(entry, entry.id|get_book_thumbnails(thumbnails)) }}
               {% if entry.id in read_book_ids %}<span class="badge read glyphicon glyphicon-ok"></span>{% endif %}
             </span>
         </a>