Amazon queries updated

Amazon has recently updated their webservices to require signed requests in the near future, so it became time to address this in my snlProtoAmazonOnca.pas unit.

The basics: parameters need to be sorted (byte, not alpha order!), properly encoded (RFC 3986 2.2), and a signature based on a special string created and appended.

This means the secret key is now needed for requests as well. Additional dependencies had to be added: I chose a HMAC/SHA256 algorithm by W. Ehrhardt and Base64 encoding by Daniel Wischnewski.

An upload will take place once I've decided the two above are really fine (license- and quality-wise).