Figure out way to hierarchically group mutation classifications and pathologic stage values

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[keller-mark]

An easy thing to do would be to just split "Mutation Classification" into multiple columns, like "Impact", "Effect", "Functional", possibly also "Amino Acid Change" and then convert the problem into a different (vueplotlib-related) problem: either "stratify by multiple variables" or "stratify by single variable but condition on the value of another"

[keller-mark]

This would also involve mutation-signatures-data changes