Clean up the .po files for this release. Plural expressions are needed in
all files that have plurals. And replace fuzzy (incorrect) translations
with empty ones instead.
This poses a small problem. We currently let translators reorder this
string, but ngettext only takes one numeric argument. This means that you
can either get correct pluralization or the order you want, but not both.
I fixed up the languages I understand at a very basic level, but the
rest will need translator assistance.
