Big refactoring to allow for additional proxy schemes that work at a
lower level than HTTP.
Introduced client-side ConnectionFactory, and binding that to a
HttpDestination, so that connections to that destination will use the
same ConnectionFactory.
The destination's ConnectionFactory is now initialized from the proxy
configuration and the transport, which is now itself a
ConnectionFactory.
The proxy configuration has also changed becoming polymorphic by
introducing a new ProxyConfiguration.Proxy abstract class,
which is implemented as HTTPProxy and can be implemented in future as
SOCKS4Proxy (and possibly others).
Merge of the branch 'http_client_transport' is now complete,
and the implementation is sound for the HTTP transport.
A basic implementation for the SPDY transport exists, but needs
improvements.
Joakim Erdfelt
Jesse McConnell
Simone Bordet
Greg Wilkins
Thomas Becker