Feature Request: Support multiple serve URL for tools

[scudette]

Currently the serve URL is chosen to be the first in the Client.server_urls list but sometimes this is not the correct URL. While the client supports switching between URLs the Generic.Utils.FetchBinary artifcat does not and the Tools mechanism does not support providing the client with multiple URLs.

We need to allow multiple URLs to be provided and support it in both the client side as the server side.

Also Generic.Utils.FetchBinary is particularly ancient now and needs updating because we dont need to support such old clients any more.