Release notes and changes for 2.0.4RC0 and 2.1.2RC0

$ ./release-doc-maker/releasedocmaker.py -p HBASE --fileversions -v 2.0.4 -l --sortorder=newer --skip-credits

$ ./release-doc-maker/releasedocmaker.py -p HBASE --fileversions -v 2.1.2 -l --sortorder=newer --skip-credits

... using yetus tagged 0.8.0

...then carefully stitched the product into the current CHANGES.md and RELEASENOTES.md files being careful to preserve markdown header ABOVE the apache license else the .md files won't render as markdown