Made sure level 5 videos would display.
Add checks for null users
This should allow things like requests and stat pages to display properly even if the database is corrupted with deleted users, by simply skipping the entries for which users are missing.

More changes to add null checks in other code paths are still to come.
Made the transcripts work!
Fixed track metadata editor dialog box.
Added error message for invalid content URLs
Transition to new translation system.
Refactor Option.isDefined checks.

Next up is Option.isEmpty, but that will likely require non-local
changes.
Further Option safety improvements.
Removing more unchecked gets
Ensure activity records are deleted with users.

TODO: Change 'actor' to 'userId'. Pretty sure that naming inconsistency
is what caused the problem in the first place. Unfortunately, this
requires a database update.
Adding robustness against ResourceLibrary errors

The resource library wrappers now all return options, to account for the
possibility that requests may fail.
Make content tiles open in a new tab/window

TODO: Ractivify the content list renderer, weed out JQuery & Mustache.
Updating translation handling
Fix Whitespace
Fix typoes