419432 - Allow to override the SslContextFactory on a per-destination
basis.

Added a new method to HttpClient, getDestination(Address, boolean,
SslContextFactory) to initialize the destination with a custom
SslContextFactory (defaulting to HttpClient's).

Also moved the initialization of the HttpExchange status to
HttpDestination.send() to allow destination.send(exchange).
Merged branch 'jetty-7' into 'jetty-8'.