Proposal: Switch to a different JSON Schema Validator

[Chris Fuller]

The experimental schema validator we currently use is the old "fge" library. This doesn't seem to be the best choice, because:

1. It doesn't appear to be maintained anymore (last release was 4 years ago).
2. There are concerns about its performance.
3. It has a lot of extraneous dependencies.

The "networknt" validator seems to address all of these concerns and still uses Apache licensing.

[Chris Fuller]

Fixed in 0.39.0