Get multiple srts to work by exposing srts at a URL, then having the video template use them.
Merge branch 'release-0.11' into multiple_srts
Fixing bug--sometimes context processors CAN be called before middleware!
Merge branch 'refactor_main' of github.com:bcipolli/ka-lite into multiple_srts

Conflicts:
	kalite/i18n/custom_context_processors.py
Fixing up more broken tests.
Fix 3 bugs: #964, #967, and that persistent cross-platform script permissions bug after unzipping
tweak the time and wording of user instructions
Merge branch 'release-0.11' of github.com:learningequality/ka-lite into 964_967
only add subtitles if they exist on disk.
central server tweaks
Merge pull request #1027 from bcipolli/optimize_wording

tweak the time and wording of user instructions
fixing inverted subtraction for shifting
Merge pull request #1021 from bcipolli/multiple_srts

Multiple subtitles support
Merge pull request #1024 from bcipolli/964_967

Fix 3 bugs: #964, #967, and that persistent cross-platform script permissions bug after unzipping
Merge pull request #1042 from bcipolli/i18n_command_tweaks

central server i18n command tweaks
fix string error in update, apply upstream django change for debugging .po files, be strict about where/how update_po is run
complete move over from jsi18n to js/i18n
get update_po to work for multiline translations
include i18n for all pages. force the catalog to be extended when testing.
adding unwrapped strings in templates and javascript files