Utility function(s) - add/remove validation data to/from existing BPX

[ejfdickinson]

Suggestion from Darryl at About:Energy, seconded by me!

• Provide a utility function that will take validation data in a suitable format (for example .csv) and merge it with an existing BPX .json. Include some sanity checking (for example, input data contain time series that are the same length of array).

• Maybe also consider a utility function that will strip validation data (or some subset of it) from the BPX .json.

Ensure that any generated BPX .json passes the schema validation in parse_bpx_file() before being returned.