Add initial languages, ready for dark-launch

Demo:
1) localhost:8080
2) Set language in browser to pt_BR
3) Refresh localhost:8080 (observe no translation)
4) Visit localhost:8080?preview-lang=pt_BR (see Portuguese)
5) Visit localhost:8080?clear-lang (see English)
6) Visit localhost:8080/admin, add new Dark Lang Config, add pt_BR to the list
7) Refresh localhost:8080 (see Portuguese)
8) Visit localhost:8080?preview-lang=ko_KR, navigate to a course (See Course Info is un-reviewed, and thus in English)
9) Append ?preview-lang=fr to same url (no french translations)