Fix naming of CHIRPS data in NetCDF

[nhsavage]

After conversion this is the ncdump:

dimensions:
	band = 1 ;
	x = 402 ;
	y = 402 ;
variables:
	int64 band(band) ;
	double x(x) ;
		x:_FillValue = NaN ;
	double y(y) ;
		y:_FillValue = NaN ;
	int64 spatial_ref ;
		spatial_ref:crs_wkt = "GEOGCS[\"WGS 84\",DATUM[\"WGS_1984\",SPHEROID[\"WGS 84\",6378137,298.25722356
...
	float band_data(band, y, x) ;
		band_data:_FillValue = NaNf ;
		band_data:TIFFTAG_DOCUMENTNAME = "/home/CHIRPS/v3.0/monthly/chirps-v3.0.2000.01.tif" ;
		band_data:TIFFTAG_IMAGEDESCRIPTION = "IDL TIFF file" ;
		band_data:TIFFTAG_SOFTWARE = "IDL 8.9.0, L3Harris Geospatial Solutions, Inc." ;
		band_data:TIFFTAG_DATETIME = "2024:11:27 17:37:12" ;
		band_data:TIFFTAG_XRESOLUTION = 100LL ;
		band_data:TIFFTAG_YRESOLUTION = 100LL ;
		band_data:TIFFTAG_RESOLUTIONUNIT = "2 (pixels/inch)" ;
		band_data:AREA_OR_POINT = "Area" ;
		band_data:add_offset = 0. ;
		band_data:scale_factor = 1. ;
		band_data:grid_mapping = "spatial_ref" ;

Fix to include units in metadata, more useful variable name and longitude and latitude not x and y