how to add a language:
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If you want to add language xy, run 
$ ./updatelang.php xy
then, translate all strings in xy/syp.php

how to update a language:
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If you want to update language xy, run 
$ ./updatelang.php xy
then, translate empty strings xy/syp.php

how to remove a language:
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If you want to remove language xy, remove xy directory, and unlink symbolic
links in root directory:
$ rm -r xy/
$ rm ../../*.xy.php

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* IMPORTANT NOTES *
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- you can split a translated string in several lines, but it must stay a php string:
  use a dot (".") to tell the php interpreter that string is not finished.