"Ability to Vary the Age of the Young Child Tax Credit Bonus (Between Ages 1-6)" feature request from Tax-Calculator

[MattHJensen]

See the full discussion: PSLmodels/Tax-Calculator#2483

An incremental approach would be to add nu01. To fully satisfy the request we would need to add nu01 through nu05.

[andersonfrailey]

This would be fairly easy to implement. I can have a PR for this open after I finish up with #363

[andersonfrailey]

To add this, there are two areas in the code that need be updated here.

For the CPS, you'll add the new age variables to this function. Then you'll need to add them to the USEABLE_VARS list here.

For the PUF, you'll add the new age variables here.

For both, you'll need to update the records_metadata.

I believe after those small updates you'll be good to go.