Univention Corporate Server 4.0 erratum 354 (bugfix)

This update addresses the following issues:
* The mapping of syntax classes to UMC widgets is now extendable via the
  UCR variable group "directory/manager/web/widget/.*/".
* In some cases ldap operations against a broken ldap connection were done
  which lead to "LDAP connection invalid" error messages. In that case the
  operation is executed again with a new ldap connection.
* The notification for successfully creating a user or computer now appears
  inside the wizard dialog.
* Opening a user is now faster.
* A link to the manual section about extended attributes has been
  added in the UMC users, groups and computers modules.