Made Grading Clearer on Progress Page

- Hid dropped markers as they were confusing users into thinking they had done something wrong.
- Added side pane to show course grade weighting more obviously to users

@marcotuts, @frrrances, @sarina, @pmitros, @shnayder - here's the PR for the progress page updates. (You don't all have to review this, but since you all commented on the design, I thought you'd like to know that this was done and under review.)

@jinpa - here's the PR for the progress page!