Student Coach Report Redesign

First pass implementation of new Student Coach Reports, as detailed in #1871.

Summary of changes:
* Create graphical display of user progress
* Only show information for subtopics that have been engaged with
* Clickable behaviour for subtopic indicators to show more detail and next steps

@aronasorman @jamie - pretty sure this is ready to merge as is, but could do with some tests, and further UX iteration.