Add translation instance

[wvengen]

It would be useful to work on translations and seeing them in Foodsoft right away.
This is possible with the localeapp integration, but perhaps Crowdin's in-context feature is more friendly. I'd like to setup a Foodsoft master instance (with just a demo foodcoop) that integrates with it, so translators can more easily work with it.

[wvengen]

Maybe nice to combine with #26.

[kidhab]

It seams like almost every changes to the language files in the past were commited directly to the Foodsofts's repository. What do you think: Is a translation instance still useful?

[wvengen]

Now and then someone comes by Crowdin and starts a new language, rarely completing it. It lowers the barrier, but as I think it takes development time, we'd better remove it. I guess we'd better make an issue in the Foodsoft repo to remove all references to Crowdin, and explain how to do translation/i18n these days.