Update configuration in iohk-nix

[sgillespie]

Recently, the configuration was updated to include settings that were previously command-line flags. We'll need to update the configurations in iohk-nix to include them, so they'll be included in playground, nix wrappers, and so on.

Note that this will not block any releasing activity, since default values are used when values are missing. This change is only to make it easier for users to update the configuration