quality.irradiance.clearsky_limits csi_max guidance

[wholmgren]

quality.irradiance.clearsky_limits includes a csi_max kwarg that should be set based on the temporal and spatial resolution of the data. It would be super helpful if the docstring included some guidance.

This is related to discussion in SolarArbiter/solarforecastarbiter-core#123, though that issue was also grappling with the intent of the filter.

cc @williamhobbs since we exchanged some notes on this.