PVLib_clearsky requires more detailed test cases

[cdeline]

In the 'aggregated_filters_for_trials' branch we've started prototyping the pvlib_clearsky filter option. As opposed to the 'dumb' csi_filter approach, there are some sophisticated analyses included in pvlib_clearsky that don't like our current test cases. To review, our degradation timeseries has a 3-year period of linear decline in power and POA irradiance from 1000 to 850 over 3 years. We might need to read in a TMY file, use that for GHI in order to allow us to use the pvlib implementation of clearsky detection...