Fixed bug.
Began refactoring.  Not yet tested.
Began major reorg.  Still undecided.
Work in progress for discussion.
Merge branch 'optional-hints2' of github.com:code-dot-org/dashboard into optional-hints2

Conflicts:
	app/models/experiment_activity.rb
Further progress.  rake test passes.
Pull global javascript variables for last AJAX response into a single hash
 - Clarify lastAjax -> lastAjaxRequest
Add helpers for unplugged / multi / match game types
Skip unplugged script levels during "next" progression
- Pull script level success AJAX response controller code out of model and into constituent helpers
- Refactor for single points of truth for various script level progression logic
- Add helper for first level in script
- Add helper for skipping invalid script levels
- Pull HoC finish URL out into a helper
- Note: WIP since doesn't account for ignoring unfinished unplugged levels during User progress resume
Add pointer to relevant method
Remove is_ from is_.(match|multi|unplugged)? methods
s/next_untried_level/next_unpassed_level
Add "add to home screen" icons for shared items
 - Add flappy icon for flappy levels
 - Add code.org logo for other shareable levels
Remove unnecessary boolean helper
Minor changes.
Adding untranslated strings from teacher dashboard
Fixed bug.
Fixed tests to work with imported Stanford hints.
Added omitted file.
fixed embedded in javascript translations