[Koha] Update translation

[Rubén Fernández Asensio]

Hello, I'd like to know the proper way of updating a translation of a 
Koha installation.
The Catalan translation of the MARC21 008 field builder is incomplete 
and I tried to expand it. I edited the file 
/usr/share/koha/intranet/htdocs/intranet-tmpl/prog/ca-ES/data/marc21_field_008.xml, 
but Koha doesn't pick it up even after Windows-style reboot, it still 
shows the old translation. What else is needed? Do I need to compile any 
PO file?

And of course, I'd like to contribute to the Catalan translation upstream.

Rubén