Add results vars

Snowpack return periods need writing outside of spinup.

T and Pr are integrated the same time windows as LSM results, and written to a forcing_integrated directory. Forcing files thus all have a month specification, e.g. forcing/forcing_1mo_195001.nc and forcing_integrated/forcing_3mo_195001.nc.

For time window = 1mo, return periods are also computed for state variable Snowpack.