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

Simple caching of get_submission() requests.

Update performance test README

One of many small pull requests that are going to come for [TIM-279].

Ignore SSL certificates for performance tests

Setting additional metadata for completing a peer workflow

Allow JSON-serializable answers

Enable django-debug-toolbar to help with AJAX requests.

Assessment Feedback Form Instruction Copy Revisions

Requires installation of Chrome extension:
https://chrome.google.com/webstore/detail/django-debug-panel/nbiajhhibgfgkjegbnflpdccejocmbbn

Add Assessment Feedback Select UI and Instructions

TIM-286

TIM-300

Copy Change: "Self Assessment" Label on Grade Report

Unlink assessment models from submission models

Use anonymous student ID if available

Fix integrity error on submission under repeatable-read mode.

TIM-271

Add management command for populating the database with dummy records.

Show Peer Scores for Each Rubric Question

Shift the creation of the peer workflow to happen when overall
workflow is created, instead of implicitly creating it if it
doesn't exist while checking for workflow status. The problem was
that the read check happens in multiple places and AJAX requests
were hitting it at the same time. Because repeatable-read mode
prevents them from seeing each others work, a couple of threads
would find that the peer workflow did not exist and would try to
create it. This cause integrity errors because those constraints
are enforced, even if those rows aren't available to other
processes.

This should have been fixed no matter what, but it's important to
note that Django should never be run under MySQL's default
repeatable-read mode. Use read-committed. For legacy reasons,
edX's own servers are misconfigured in this respect.

[TIM-262]

TIM-287

Disable template caching