Updated PR for passing CO2 flux from fates

[mvdebolskiy]

These changes introduce the capability for FATES to write NBP (net biome productivity) fluxes to the atmosphere, inclusive of fire, harvest, grazing and product pool decay carbon flux.

This PR is linked to the CTSM-side PR (NorESMhub/CTSM#140)

Noting that this code neither creates nor passes the gridcell level balance check on account of timestepping complexities that need to be resolved in a later PR., likely NGEET#137

To recall:
NBP =.NEP - C_fire - C_grazing - C_productdecay

where fire and grazing fluxes are now output from FATES, and product decay (a gridcell property) is calculated in CTSM.

NEP is the Net Ecosystem Productivity, defined as
NEP = GPP - Reco

where GPP is the gross photosynthetic productivity and Reco is total ecosystem respiration inclusive of plant (Rauto) and soil (Rh)

Collaborators:

@ckoven
@maritsandstad
@mvdebolskiy
@rgknox

Only updated to sci1.85.1-api40