We use the filename format gbb_${BOARD}_${HWID} for GBB blob files and
place them in the same directory of site_tests/factory_WriteGBB, but in
private git.
Actually, these files will be automatically put in the factory image.
This change is to remove those not belonging to the same board.
Also do some fixes and rename QualDbs stuffs.
TEST=run image_to_usb.sh and check the gbb files.
BUG=chrome-os-partner:789
Change-Id: I5913a14eb3ceef5abfdf1a87156faa6bb7dbd561
Review URL: http://codereview.chromium.org/3111014
