implement password change for mailboxes

- implement managemails.forms.ChangeMailboxPasswordForm
- extract code for determining hosting package and customer from URL into
  HostingPackageAndCustomerMixin
- implement managemails.views.ChangeMailboxPassword
- add new URL pattern 'change_mailbox_password' to managemails.urls
- add template managemails/mailbox_setpassword.html
- link from template hostingpackages/customerhostingpackage_detail.html to
  change_mailbox_password
- add german translation for new strings
- document new feature in changelog

gnuviechadmin/managemails/locale/de/LC_MESSAGES/django.po

@@ -7,8 +7,8 @@ msgid ""
 msgstr ""
 "Project-Id-Version: managemails\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2015-01-25 12:04+0100\n"
-"PO-Revision-Date: 2015-01-25 12:07+0100\n"
+"POT-Creation-Date: 2015-01-25 12:46+0100\n"
+"PO-Revision-Date: 2015-01-25 12:47+0100\n"
 "Last-Translator: Jan Dittberner <jan@dittberner.info>\n"
 "Language-Team: Jan Dittberner <jan@dittberner.info>\n"
 "Language: de\n"
@@ -51,6 +51,10 @@ msgstr "Postfächer und E-Mailadressen"
 msgid "Create mailbox"
 msgstr "Postfach anlegen"
 
+#: managemails/forms.py:69
+msgid "Set password"
+msgstr "Passwort setzen"
+
 #: managemails/models.py:79
 msgid "Mailbox"
 msgstr "Postfach"
@@ -75,11 +79,17 @@ msgstr "E-Mailadresse"
 msgid "mailbox"
 msgstr "Postfach"
 
-#: managemails/views.py:35
+#: managemails/views.py:63
 msgid "You are not allowed to add more mailboxes to this hosting package"
 msgstr "Sie können keine weiteren Postfächer zu diesem Hostingpaket hinzufügen"
 
-#: managemails/views.py:61
+#: managemails/views.py:82
 #, python-brace-format
 msgid "Mailbox {mailbox} created successfully."
 msgstr "Postfach {mailbox} erfolgreich angelegt."
+
+#: managemails/views.py:117
+#, python-brace-format
+msgid "Successfully set new password for mailbox {mailbox}."
+msgstr ""
+"Für das Postfach {mailbox} wurde erfolgreich ein neues Passwort gesetzt."