Import language files from mozilla-central

[timvandermeij]

We should import language files from mozilla-central. We could try to look for a way to import them automatically such that all language changes can be done at a central place. This seems necessary to me because the language files here have different layouts and are not all up-to-date. That also saves double translation work.

They can be found here: https://mxr.mozilla.org/l10n-mozilla-release/source/nl/browser/pdfviewer/viewer.properties

[timvandermeij]

I'm currently writing a Makefile extension for this. See timvandermeij@65b74b4. Not ready yet, but work in progress :)

The goal is to make it fetch all translations from mozilla-central, but keep our metadata.inc files. All translations would therefore need to be done at mozilla-central and not here anymore (since it will be overwritten) such that it's more centered and no double work is done. On top of that, mozilla-central has a lot more translations that we can then ship with PDF.js, so it's a win-win situation.

[Snuffleupagus]

If we are going to import files from mozcentral, we should probably use the most updated ones, i.e. the translations used in the Nightly versions: http://mxr.mozilla.org/l10n-central/source/.