Correction of dsr and usr filters out daily transmission

[BaptisteVandecrux]

There's a range check on dsr and usr that removes "invalid" data:

pypromice/src/pypromice/process/L1toL2.py

Lines 159 to 163 in 6ad5893

	# Remove data where TOA shortwave radiation invalid
	isr_toa = calcTOA(ZenithAngle_deg, ZenithAngle_rad) # Calculate TOA shortwave radiation
	TOA_crit_nopass = (ds['dsr_cor'] > (0.9 * isr_toa + 10)) # Determine filter
	ds['dsr_cor'][TOA_crit_nopass] = np.nan # Apply filter and interpolate
	ds['usr_cor'][TOA_crit_nopass] = np.nan

The problem is that for stations that:

• had a problem with their loggers and therefore only transmissions are available
• start to have sunlight before the logger program switches to hourly transmission
  then we have daily average shortwave radiation instead of hourly values.

These daily values are lower than the hourly values and are removed from dsr_cor an usr_cor.

This range-check should therefore be done only on hourly values.