(implemented, discussion locked) Distributions as parameters to other distributions.

[Hazelfire]

Currently, distributions only support floats as parameters. However, it would be valuable in some cases to have distributions as input types.

I came across an example in my GiveDirectly model. In this model, the mean household size (which was already a distribution of mean household sizes) was needed to calculate the distribution of mean baseline income. I compromise by getting the mean of the estimate of means of household sizes. This is not a large compromise in this instance, because the variance of household sizes is really low, but I can imagine other cases where this could become an issue.

[quinn-dougherty]

This made it in, so we're locking this convo