Implement aggregation for array items
Something for aggregating (for example) this:
num_by_quals: [235, 135, 1241, 51]`
into this:
num_by_quals: [
{count: ..., max: ..., min: ..., mean: ..., median: ..., stdev: ...},
{count: ..., max: ..., min: ..., mean: ..., median: ..., stdev: ...},
{count: ..., max: ..., min: ..., mean: ..., median: ..., stdev: ...},
{count: ..., max: ..., min: ..., mean: ..., median: ..., stdev: ...},
]