Add module-temperature/irradiance correlation check

[wfvining]

PVFleets QA checks that the module temperature is correlated with the irradiance. This is a pass/fail quality check: if the temperature and irradiance have sufficiently high correlation over the entire series then the temperature sensor passes. It might be useful to apply the correlation check on rolling windows as well and return a boolean series rather than just a pass/fail.

I'm not sure where this should go in the quality module.