Warn user if no videos are available for that language.
Clear the "Loading topic tree" text and be more apologetic in language
Tweak apology language some more, avoid inserting raw html tags
Merge pull request #1515 from aronasorman/1464

Warn user if no videos are available for that language.
do not clobber other get parameters when changing the users language
remove unused js CHANGE_*LANGUAGE_URL variables
fix the set_user_language get parameter
add zip download size when upgrading