Clean up paths & structure across files, to share more, assume less.
Remove subtitle map from repo.
Make dubbed video map have a graceful fallback.
Small documentation changes.
Merge branch 'develop' of github.com:learningequality/ka-lite into i18n_cleanup_2

Conflicts:
	kalite/management/commands/zip_kalite.py
Merge pull request #1285 from bcipolli/i18n_cleanup_2

I18n cleanup 2