Fix for #1237: allow users to set their own default language.
Fix for #1158: eliminate need for LanguagePack model (but keep the model, for future use)
remove base.html code for setting as default--taken care of implicitly now.
removing admin display of language packs, since they are empty
Localize the reloading of session data, to avoid programming errors.
Merge pull request #1278 from bcipolli/1237

Fix for #1237: allow users to set their own default language.
Partial fix for #1273: avoid errors if no zip/po files exist for a given language.
Merge pull request #1279 from bcipolli/1158

Fix for #1158: eliminate the need for the LanguagePack model
do not include crowdin-cached files in KA Lite zip
Clean up paths & structure across files, to share more, assume less.
Remove subtitle map from repo.
Make dubbed video map have a graceful fallback.
fix issue #1251: remove calls to sudo in scrape_videos
place youtube-dl in /scripts instead of /data/scripts
Merge pull request #1283 from aronasorman/1251

fix issue #1251: remove calls to sudo in scrape_videos
Small documentation changes.
Merge branch 'develop' of github.com:learningequality/ka-lite into i18n_cleanup_2

Conflicts:
	kalite/management/commands/zip_kalite.py
Merge branch 'i18n_cleanup_2' into 1164

Conflicts:
	kalite/i18n/management/commands/generate_subtitle_map.py
	kalite/i18n/management/commands/update_language_packs.py
	kalite/management/commands/zip_kalite.py