Derive constants c1 and c2

[ecowan]

By Abadi et al. theorem 1 (pg. 4) we can choose constants c1 and c2 such that sigma will guarantee differential privacy

[ecowan]

From Theorem 1 (pg. 14) we have a DP guarantee provided that

1. T * q^2 * lambda^2 / sigma^2 <= lamba * epsilon / 2
2. exp(-lambda * epsilon / 2) <= delta

So given epsilon and delta from the inputs to the function, we need to find the optimal sigma (noise scale) to satisfy (1) and also verify that (2) is satisfied.

[ecowan]

I believe this can be merged in with #313