Check GGCMI's ISIMIP Phase 3b group III crop calendar input files

Things checked for all files:

• File has "Crop" attribute
• Values are within acceptable bounds: all variables except growing_period, planting_day-mavg-window, and seasonality.

Things checked for files of crops that have the growing season algorithm applied (mai, ri1, sor, soy, swh, wwh):

• Every variable is constant within each decade (including both NaN masks and actual values)
• Every variable does vary over time (except for seasonality)

Things checked for files of other crops:

• Every variable is constant over time