Prevents requirejs error with perseus exercises loaded.
Fixes #2529
Fixes khan contentload bug. Adds paths to denormed exercise and videos.
Fixes soundmanager to no longer use require js.
Allow content viewing without being logged in.
DRYs up content rendering with no content log available.
Further restricts lockdown. Reduce homepage to link to 'learn'.
Merge pull request #2534 from rtibbles/login_issues

Content rendering fixes
Fixes contentload to properly use channel_name as root node path.
Makes search autocomplete properly function for all imported content.
Fixes #2541. Generate urls for 'learn' from search page.
Makes search single match results properly direct to learn tab.
Fixes contentload test.