Adapt to the big <Card> redesign.
Also, as part of 19.0.0, the shadow variables in paragon got
marked as !default, letting the theme override them. This would
normally be fine and good. But the edx.org theme has a dramatically
larger shadow set. And a lot of our cards and card-like components
were designed with a smaller shadow in mind. So I added a new
raised-card custom css class to keep as many cards looking the same.
Notably, I cannot fix the data tables on the Progress tab. So those
might have a larger shadow with this change, but that's unavoidable
and presumably the intent of the edx.org theme authors.
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