Merge pull request #2 from intgr/allcdcovers

Script to upload cover images from allcdcovers.com
[barcode_scanner] Initial import. Also changed _edit_release_information to return the result
[barcode_scanner] Also scan Obi covers, enable EAN-8/UPC-A/UPC-E and ISBN support
[allcdcovers] Enable EAN-8/UPC-A/UPC-E and ISBN barcode support like barcode_scanner
[barcode_scanner] Don't die on image corruption errors; add art type to edit notes; better output
[barcode_scanner] Don't log into MusicBrainz when there's nothing to do
[barcode_scanner] Add Code 39 barcodes to annotation
[barcode_scanner] Don't scan images that have pending edits