Remove the NoData value from the QA bands about ledaps HOT 4 CLOSED

You could add appropriate ENVI header tags and colors for this. These would 
cause ArcGIS to load in the information properly.  Here's an example of some 
tags I add to Fmask files:

class lookup = {0, 255, 0, 0, 0, 255, 127, 127, 127, 0, 255, 255, 255, 255, 
255, 0, 0, 0}
class names = {Clear land, Clear water, Cloud shadow, Snow/ ice, Cloud, No data}

It would be similarly helpful to add acquisition time, wavelength, wavelength 
units, and FWHM tags to ENVI header files.

Guy, thanks for your solution for cfmask classes. I will pass that along, and 
also consider using these class lookup/names for the ENVI headers of the LEDAPS 
QA products.

The NoData values for the QA values still needs to disappear, since the NoData 
pixels really aren't flagged separately in these QA bands.  The fill band 
specifies the NoData pixels.  This will require a change to the XML scheme, 
since the fill_value is a required value for the metadata.

The ignore data value has been removed from the ENVI header for the surface 
reflectance QA bands.  The fill_value has been switched to an optional value in 
the ESPA schema, and the fill_value is no longer written as a band-related 
parameter for the QA bands.