Removing LanguagePack from models/database.
Remove unnecessary management commands (distributed server).
Remove unnecessary functions and api endpoints.
Moving functions specific to language pack download to languagepackdownload.py
Updating management command params to default properly on distributed server.
Removing bogus imports from languagepackdownload
Remove central server command from distributed app.
Remove central server paths and functions from i18n app.
Remove outdated parameter is_central_server
Merge pull request #1737 from bcipolli/i18n-refactoring

I18n refactoring