Add sectional scheme for NPF as compset option

[sarambl]

This merge contains the sectional scheme developed in Blichner et al (2021a) as a compset option. Various tests have been performed (see https://github.com/sarambl/IMP_SEC_CAM-Nor) to check that the default scheme is not impacted and that the restart works as expected. Additionally, in Blichner et al (2021b), we estimate the changes to ERFaci and ERFari.

Feel free to request changes or additional tests/documentation etc or changes before pulling the code!

References

• Blichner, S. M., Sporre, M. K., Makkonen, R., & Berntsen, T. K. (2021a). Implementing a sectional scheme for early aerosol growth from new particle formation in the Norwegian Earth System Model v2: Comparison to observations and climate impacts. Geoscientific Model Development, 14(6), 3335–3359. https://doi.org/10.5194/gmd-14-3335-2021
• Blichner, S. M., Sporre, M. K., & Berntsen, T. K. (2021b). Reduced effective radiative forcing from cloud–aerosol interactions (ERFaci) with improved treatment of early aerosol growth in an Earth system model. Atmospheric Chemistry and Physics, 21(23), 17243–17265. https://doi.org/10.5194/acp-21-17243-2021

[oyvindseland]

Included in commit 9271f1d38e25447237be4ab5d028decfa5eef295