Move openassessment out of the apps directory
Use pkg_resources to check whether OA XBlock is installed.

Added management command to upload archive of CSV data to S3
Add a scenario with unicode in all rubric strings
Add tests for unicode CSV reports
Added progress indicator to upload management command
Optimize database queries for CSV reports.
Fix issue with duplicate assessment feedback options.

This introduces a few features:
* INFO level logging on common events like creating or fetching
  submissions and assessments.
* Parallel event logging for the same.
* Creates a local logs/ directory for development.

For the most part, we rely on XBlock's publish() mechanism to emit
event data. However, because scoring is done at the API layer in a way
that is not directly visible to the OpenAssesmentBlock, we're logging
that event separately with a hacky solution that dynamically loads an
emit function based on a configuration value. This is a stopgap
measure until we can start using the edX analytics API (which is still
in testing).

TIM-260, TIM-378

This reverts commit e0f5a8aa.

Conflicts:
	apps/openassessment/management/tests/test_create_oa_submission.py

[TIM-202]

* Basic parsing of XML rubric's in @ormsbee's proposed format
* Rubrics displayed to user after they've made at least one submission
* Multiple rubrics on the workbench with different evaluation criteria

We're not aiming to have an REST API in the MVP. Can re-add when
we get around to implementing it.