Provide feedback in peer assessment

[TIM-230](https://edx-wiki.atlassian.net/browse/TIM-230)

Some notes:
* I did not include tests for `OpenAssessment.BaseUI` (JS) as I expect this will need to change as we hook it up to the workflow.
* JavaScript errors are sent to `console.log` for now, until there is a place in the UI for them to go.
* The grade template contains some dummy tags so I could verify that the flow was working, which should be overwritten by @talbs 

@stephensanchez