New po/README

[John Mandereau]

Hello translators,

I've written a README to clarify program strings PO files (po/*.po)
should be translated only via the Free Translation Project, so we no
longer commit such translations directly to the sources like I or other
translators in the past.

Btw, Till, have you got news for the improvements you'd like to be made
on de.po?  I really don't want your work to be lost, and the better way
would be to make FTP lanugage team accept it.

Best,
John