Write an executable that will produce the ledger cost models from our cost models

mpj wrote:

We want to be able to easily give the ledger updated versions of the cost model that they can use, i.e. in an ordered list of parameters.

We may want to update any of the ledger languages, so we should be able to produce the cost model for any language.

Probably best if we explicitly feed in the cost model files, rather than always using defaultCostModel.json. Or allow either.