Removed dead code

(this is no longer needed now that we're using the SKU field... don't
need to add a variant by the metafields anymore)
Added helper method for generating SKUs

also added barcode field for the physical media
Replaced GUID with SKU
Batch file for running in test mode
Merge pull request #11 from PhilipDavis/master

Updated the tools to use SKU fields instead of storing a GUID in metafields