Output timeseries data as CSV

[ledm]

I need to extract the output time series data and write it as csv files so I can do it outside of bgcval2. The csv (or mauybe json?) format should be a lot more portable than shelve files.

Probably best open will be to add a "save_as_csv" option into the input.yml file.

In addition to the two columns (time and value), I'd like to include the wider metadata, maybe as a header, including the jobID, region, layer, metric, time shift, line colour and style. That kind of thing would be useful to ensure that the secondairy plots are consistent with bgcval2 output.

[ledm]

Working on this now. It'll need json and a new package jsondiff. I think this is why the tests have been failing.