Amazon-based music store

We now have a music store, absed on the Amazon catalogue.

Searching works for DE, FR, JP, UK, US. Checking items out is broken atm
for US, but should work in a few days after we get a ok from Amazon.

Not yet implemented:
* viewing the shopping cart in Amarok
* limiting search to albums/tracks only
* track previews
* you might also see some albums without a price
* artwork is still missing.


DIGEST: Amazon-based music store in Amarok