log to the structured log when starting and finishing an activity
Merge pull request #390 from code-dot-org/activity-slog

log to the structured log when starting and finishing an activity
fix builder script.

Conflicts:
	lib/tasks/seed.rake
- Tests
- Add maze level builder (artist already exists.)
- Add toolbox, start blocks, and required blocks editor.
- Add maze builder.
- Name cancan fix before_filter so we can skip it where needed.
- Improve level editor form.
- Abstract some setup code so both script_level controller and levels controller can present levels in a similar way.
- Fix passing blocks to blockly if when there aren't any
- Use create action as entry point instead of custom actions.
- Fix start blocks to be able to see more of them.
- Only show blocks which for with the app being edited.
- Do a redirect upon custom turtle level (maze is already this way).
Remove script/stage changes.
Undo more script changes.
Fix mode -> model.
Remove reference to old table.
- send auth token with ajax so we don't have to skip it in the controller.
- boolean zen.
Fixed levels helper and wrote a test.
Fix schema for nonnull stuff. Fix rake task to use transaction.

Clean up tests.
add fixed ids
Fix rake task.
Merge pull request #382 from code-dot-org/toolbox

- Tests
Add back CustomMaze game which got lost in conflict resolution.
Merge pull request #393 from code-dot-org/toolbox

Add back CustomMaze game which got lost in conflict resolution.
Merge pull request #394 from code-dot-org/finished

Deliver finished.