Revert "Removes unused record group ID field."
Revert "Removes unused record group ID field."

This reverts commit c27c1d77d2164c7361f1094bddf6fdc05d5e3e01.

It turns out -- the record group ID field is being used. To
remove it, we'll need to modify code in ADAM as well. I'm
just going to revert this for now.

ryan-williams/bdg-formats,bigdatagenomics/bdg-formats,GELOG/bdg-formats,heuermh/bdg-formats,erictu/bdg-formats