Update and enable the document comments app

apps/document_comments/registry.py

@@ -0,0 +1,10 @@
+from __future__ import absolute_import
+
+from django.utils.translation import ugettext_lazy as _
+
+from .icons import icon_comments_for_document
+
+label = _(u'Comments')
+description = _(u'Handles document comments.')
+icon = icon_comments_for_document
+dependencies = ['app_registry', 'icons', 'documents', 'permissions', 'navigation']