Resolve "Update open edx translation files to Koa version"

Closes #45 (closed)

I downloaded the Koa translation files for French, Spanish, Arabic and Farsi from transifex and added them to the repo. I rebuilt the platform to see if they work. I could see that French has some additional translations on the registration page that are not translated on the live platform, so I assume success.

I had to fix some translation strings in Arabic and pushed those back to transifex.