Move a bunch of logic here from soup-context. Now the session keeps track

Move a bunch of logic here from soup-context. Now the session keeps track

	* libsoup/soup-session.c: Move a bunch of logic here from
	soup-context. Now the session keeps track of hosts (instead of
	having a global soup_hosts hash) and their connections.
	(soup_session_new_with_proxy, soup_session_new_full): New session
	constructors to specify a proxy or a proxy and connection limits
	(send_request): Add Authorization and Proxy-Authorization headers
	before sending off the request.
	(soup_session_queue_message, et al): Improve the way this works.
	There's no need to use timeouts to wait for connections to become
	free; we *know* when they become free.

	* libsoup/soup-private.h: Remove SoupHost and some other
	no-longer-used stuff.

	* libsoup/soup-misc.c (soup_set_proxy, soup_get_proxy,
	soup_set_connection_limit, soup_set_connection_limit): Gone. These
	are all per-session now.

	* libsoup/soup-message.c: Remove all SoupContext references
	(mostly replaced with SoupUri references)
	(cleanup_message): priv->connect_tag and priv->connection are gone
	now, so this was just soup_message_io_cancel(). So remove
	cleanup_message and replace it with that everywhere.
	(soup_message_disconnect): Gone.
	(soup_message_set_uri): Replaces soup_message_set_context.
	(soup_message_set_connection, soup_message_get_connection): Gone

	* libsoup/soup-message-server-io.c (parse_request_headers):
	s/soup_message_set_context/soup_message_set_uri/

	* libsoup/soup-message-private.h (SoupMessagePrivate): Remove
	connect_tag, context, and connection.

	* libsoup/soup-message-client-io.c (encode_http_auth): Gone.

	* libsoup/soup-context.c: Gone

	* tests/auth-test.c (identify_auth): update for session/context
	changes