Separate Credentials for GerTranslateWebServer

[magula]

We should use different credentials for every team in GerTranslateWebServer in the future.

This could easily be done by using NGINX HTTP auth. Every path beginning with /[lan]/ would be protected by its own password file. Thus we should write a script to create

1. a password file user_[lan] for each team (language) and
2. an NGINX site that restricts access to /[lan]/ to the authentication with user_[lan].

GerTranslateWebServer is already designed with this in mind and therefore uses an appropriate scheme, but some changes may be necessary. It should be ensured that all teamleaders can still see the other teams' translations, so working together is not hindered between teams nor between the teamleaders of one team.