DPArgMax, DPArgMin, DPSVT (2)

[Shoeboxam]

When data passes through mechanisms, the mechanism switches the releasable property to true. Currently the runtime releases anything with releasable set to true. Going forward, there could be an extra property, hidden that prevents releasable data from initially being released, and a property privacy_usage with the amount of budget to charge once the hidden bool is unset.

This could be paired with:

1. components DPArgMax, DPArgMin, DPSVT that construct a differentially private boolean mask or index set from private data.
2. the current Index component that can filter columns from multicolumnar arrays
3. some component to publicize the data... just flip the hidden bit.

So for instance, both LaplaceMechanism and DPArgMin take in the output from some aggregator. Interestingly, if we have a non-private model builder, you could also reuse Index, DPArgMax to find a best subset of predictors. Or technically if you have the data, you could compute scores on your own, and then just ask for a DPArgMax. This design would also be able to filter columns from grouped releases.

[Shoeboxam]

e75b1eb was meant to reference #113, not #103