This uses the new FilePermission framework to set permissions on the
directory holding the database files. The new config attribute
ds-cfg-backend-mode is optional and by default has a value of 700. The
permissions are set on backend initialization as well as on the fly via
LDAP. The server will make sure the file permissions will allow owner
access before setting. Any exceptions encountered while setting the
attribute will result in non fatal errors which are logged. However, any
configuration exceptions will keep the backend from starting.

Fix for issue 50