Reset submission API scores in beta and legacy instructor dash

[TIM-267](https://edx-wiki.atlassian.net/browse/TIM-267)

Note that this depends on a PR in edx-ora2 that has not yet been merged:
https://github.com/edx/edx-ora2/pull/269

I'm a little concerned that the location we're getting from `StudentModule` could get out of sync with the scope ID we get from the XBlock.  In particular, I'm worried about the location/locators refactor and AB-testing.  I'd appreciate some input from the LMS team about this, so feel free to tag folks who might know more.

@ormsbee @sarina