Merge branch 'update_language_tweaks' of github.com:bcipolli/ka-lite into release-0.11.1
Too much for one commit, but inseparable at this point.  Includes: localizing shared constants to shared/i18n, shortening names, decreasing non-debug output, closing file pointers when done, indenting changes, removing API keys from public code, and being explicit about language code formats.
Fix #1138 (move data files to internal data directory), fixed a copule of small bugs.
Validating languages, making internal storage for cache_subtitles use IETF standard, and django to use its own standard.
More refactoring, variable renaming, cleaning--and a few key changes to make use of lang_code (ietf vs django) more obvious and consistent
Merge branch 'release-0.11.1' of github.com:learningequality/ka-lite into lang_code_consistency
Merge branch 'release-0.11' of github.com:learningequality/ka-lite into lang_code_consistency
Fixing bug in branch code and in languagepackdownload code.
removing duplicate language pack defs
just because a srts exist doesn't mean a language pack is available for download.
Merge branch 'release-0.11.1' of github.com:learningequality/ka-lite into lang_code_consistency
removing my old friend
fix issue #1136: Show installed languages in the update videos page.
compress language packs--srts are text
reorganize available language packs text in /update/videos
fix issue #1137: Add english to list of languages if we don't have a
language pack for it
Don't show "set as default" link if language is already set as default
Merge branch 'release-0.11.1' of github.com:learningequality/ka-lite into lang_code_consistency
Multitude of fixes to central server pages and styling.
After server start, load a page silently to avoid a delay on first view

Will fail silently (without issue) if curl is not installed.