Extend VARIABLE_MAP with remaining NASA POWER parameters, fix dew point naming

Author: karlhillx

pvlib/iotools/nasa_power.py

@@ -18,11 +18,15 @@
     'T2M': 'temp_air',
     'WS2M': 'wind_speed_2m',
     'WS10M': 'wind_speed',
-    'T2MDEW': 'dew_point',
-    'T2MWET': 'dew_frost_point',
-    'TQV': 'precipitable_water',
+    'ALLSKY_SFC_LW_DWN': 'longwave_down',
+    'ALLSKY_TOA_SW_DWN': 'ghi_extra',
+    'CLRSKY_DIFF': 'dhi_clear',
+    'PS': 'pressure',
+    'T2MDEW': 'temp_dew',
+    'T2MWET': 'temp_dew',
     'RH2M': 'relative_humidity',
-    'ALLSKY_SRF_ALB': 'albedo',
+    'SRF_ALB': 'albedo',
+    'TQV': 'precipitable_water',
 }