Add translation status script and template page

Add translation status script and template page

This stuff is in rough draft state, but it works.

To test it, cd into Documentation/ and do

python ../buildscripts/translations-status.py ../buildscripts po/out-www

this will leave out Documentation/translations.html.in -- please do
not add this file to Git right now, because we do not want to make
translation status info widely available until translators all agree
about it.