New improved Dutch translation for Abiword 2.9

See the attached file.

Note: it appears that there's a coding error in the msgid in line 60: it's
supposed to literally show the percentage of normale size:
msgid "% of normal size"

However, the % sign is erroneously being interpreted as a code meaning
something else, in conjunction with the "o" of "of". msgfmt demands
that this error be reproduced in the msgstr in line 61.

So I've worked around it:
msgstr "% o percentage van normale grootte"

In the translated msgstr, the "% o" part is now meaningless and
superfluous, but at least msgfmt appears to be satisfied.

However, a fix would be better than a workaround.

Regards, Pjotr.