Feature Request: improve scanning and adding of books in different languages

[GoogleCodeExporter]

My personal library contains both german and english books. Having the locale 
set to German (as default), I can't "scan and add" english books. Any attempt 
results in a misleading message, saying that the book can't be added because it 
might already be in the collection.

Just by chance I changed the locale setting within Shelves to "US" and to my 
surprise, it recognized all my english books.

Practically spoken, it's rather complicated to change Shelves settings 
according to the language of the book you want to scan.

I suggest removing this limitation. Shelves could try to find a book in many 
languages, ISBN numbers should be unique, it might even try to guess the 
language based on ISBN an choose the best lookup service.

Original issue reported on code.google.com by andreas....@googlemail.com on 8 Aug 2010 at 1:38