369: update multiple-choice stats to handle new stats data format

- Updated the Stats Multiple Choice Question bric to expect 'Correct' and 'Incorrect' as response codes instead of 'correct' and 'incorrect'

- Updated the aggregateData objects in the Stats Multiple Choice Question bric unit tests and templates to match DAALT's new API (from the spec not from any supplied example)

The API can be found in the [DAALT Data Services Contract, Section 1.11](https://docs.google.com/a/pearson.com/document/d/1dUT7vZstHFssOPAVnpOfuuzj_V6htmIaT4AORJCP8WI/edit#heading=h.5e6yj2zhwu1q) 'learning_resource_to_items'

Jira: BRIX-369
Added notes to doc/CreatingNewBrix.md concerning updating the presenterTypesHash when adding a new presenter