Reverting function to previous (functioning) state.
Search box uses custom button, avoiding cross-browser styling nightmare.
Merge pull request #1160 from jamalex/tweaks_from_nalanda_testing

Several tweaks to address issues identified during Nalanda testing
Added build id to static paths for some CSS/JS files that have changed.
Merge branch 'release-0.11.1' into search_box_tweaks
Merge pull request #1153 from bcipolli/dubbed_video_choice

Select dubbed videos via topic page clicking.
Merge pull request #1162 from jamalex/prevent_static_file_caching

Added build id to static paths for some CSS/JS files that have changed.
Merge pull request #1163 from jamalex/search_box_tweaks

Search box tweaks: replaced button for search box with custom button
Added Web Of Trust verification
Merge branch 'release-0.11.1' of https://github.com/learningequality/ka-lite into release-0.11.1
remove empty start callback
use sprintf.js
Only count videos in topic calculation; compute (relevant) video urls only for exercise, video, and "bottom level" topics
"bottom-level" topics should not say they contain topics--they don't!
in a rush, it's Thanksgiving.
refactor -- place both adding installed languages and showing
installable languages into a single function
cleanup on some use of sprintf
Merge pull request #1169 from bcipolli/efficient_url_computations

Efficient url computations
factor out code that starts language pack download into its own function
solve issue #1118: Add upgrade link if a central server version is higher