Allow netcdf output

[K20shores]

In python, outputting to netcdf is dead simple as long as xarray is installed

import pandas as pd
import xarray as xr

df = pd.read_csv('ouput.csv')
df.set_index(['time']).to_xarray().to_netcdf('output.nc')
ds = df.set_index(['time']).to_xarray()
ds['CONC.ALKNIT'].attrs = {'units': 'mol m-3'}

Acceptance criteria

• A new command line option --output-format is present.
  • options are csv and netcdf
  • default to csv
  • when the output format is netcdf and the -o option is not provided, write the results into the current directory. Do not print the csv output
• In netcdf output, units of all species and environmental conditions are added
  • integrated reaction rates (anything with irr_ in the name) have units of mol m-3
  • any attributes of species from the species.json file should be added to the attrs for that species
• Csv headers include units as an .units, which would close Descriptive output file names or add units to header #143
  • For example, CONC.ALKNIT.mol m-3
• All output code (csv, netcdf, printing termainl, whatever), is located in one file

Ideas

• Perhaps conforming to CF conventions could be nice, at least in terms of metadata on the variables like units, name, description, etc.
  • The description could be read from the species.json, as well as any other information stores in the json files
• Abstract file output to a new function (or class, whatever) that takes in the command line arguments and determines which output format. When going to netcdf, do the extra work of adding units and as much detail as possible to everything