add list, delete and edit comment of SSH public keys

- add sshkeys to hostingpackage detail view context
- implement new osusers.forms.EditSshPublicKeyCommentForm
- implement new views ListSshPublicKeys, DeleteSshPublicKey and
  EditSshPublicKeyComment
- add new URL patterns 'list_ssh_keys', 'edit_ssh_key_comment' and
  'delete_ssh_key'
- link from hosting package detail view to 'list_ssh_keys' when there are
  SSH keys assigned to the shown hosting package
- add new templates osusers/sshpublickey_list.html,
  osusers/sshpublickey_confirm_delete.html and
  osusers/sshpublickey_edit_comment
- add operating system user output to template
  osusers/sshpublickey_create.html
- add changelog entry

gnuviechadmin/templates/hostingpackages/customerhostingpackage_detail.html

@@ -39,7 +39,7 @@
         <dd>{% blocktrans with num=hostingpackage.used_mailbox_count total=hostingpackage.mailbox_count %}{{ num }} of {{ total }} in use{% endblocktrans %} <span class="glyphicon
         glyphicon-info-sign" title="{% blocktrans with mailboxcount=hostingpackage.mailboxcount %}The package provides {{ mailboxcount }} mailboxes the difference comes from mailbox options.{% endblocktrans %}"></span></dd>
         <dt>{% if osuser.is_sftp_user %}{% trans "SFTP username" %}{% else %}{% trans "SSH/SFTP username" %}{% endif %}</dt>
-        <dd>{{ osuser.username }}</dd>
+        <dd>{{ osuser.username }}{% if sshkeys %} <a href="{% url 'list_ssh_keys' package=hostingpackage.id %}" class="badge" title="{% blocktrans count counter=sshkeys|length %}There is an SSH public key set for this user.{% plural %}There are {{ counter }} SSH public keys set for this user.{% endblocktrans %}"><i class="fa fa-key"></i> {{ sshkeys|length }}</a>{% endif %}</dd>
         <dt>{% trans "Upload server" %}</dt>
         <dd>{{ uploadserver }}</dd>
       </dl>