QA Value Modification to include Fill in each band

```
Initiated by Junchang Ju's observations, and maybe not a bad idea to consider 
for future implementation.

Ideally in the one-byte QA mask bands, 0 can be for “absence”, and 1 for 
“presence”, and 255 for fill value

```

Original issue reported on code.google.com by `kallie...@gmail.com` on 9 Mar 2015 at 1:53
