Tiny copy changes

Optimizations to the PeerWorkflow and PeerWorkflowItem models

Improving performance and model definitions with clear foreign keys associated with the peer workflow behavior.

Reducing query count

Prevent workflow from trying to create multiple scores for the same user

Make it so that create_assessment returns the same (cached) data structures that get_assessment(s) returns.

Update fixtures for new submission field format

Check whether Node is installed

Remove minor redundant queries for checking number of peer assessments associated with a peer workflow.

a submission from 3 to 1.

Bypass REST framework serializer validation for assessment part creation (we validate before anyway).

Stop waiting for peers to assess before logging in as a new user

Create submissions command uses same JSON format as the XBlock

Update test for the circular import fix

Fix circular import

Fix metadata editor template error in Studio

Fix warning for submission in Studio preview

Make django-debug-toolbar >= 1.0 work properly with syncdb and admin.

The autodiscovery used by admin will interact badly with Django
Debug Toolbar's own auto-setup. So we have to be more explicit about
everything and add some settings manually. See:

http://django-debug-toolbar.readthedocs.org/en/1.0/installation.html#explicit-setup