Dutch language file updated.

Hi Greg,

I have updated the Dutch language file. But when saving the po-file an error occurs:

'Error: duplicate message definition'.

It turned out to be the part below that causes the error:

#: help_text.php:510
msgid "Quick family facts"
msgstr "Snel toe te voegen feiten/gebeurtenissen voor gezinnen"

#: admin_trees_config.php:1137
msgid "Quick family facts"
msgstr ""

I have solved this error for the Dutch file, but I checked a few other po-files and they all have the same error.