Added https support with Net implementation.

Added notion of default HTTP_CLIENT, to be able to build portable code among http client implementation.

library/network/http_client/src/default/libcurl/default_http_client.e

@@ -0,0 +1,15 @@
+note
+	description: "[
+			Default HTTP_CLIENT based on LIBCURL_HTTP_CLIENT.
+		]"
+	author: "$Author$"
+	date: "$Date$"
+	revision: "$Revision$"
+
+class
+	DEFAULT_HTTP_CLIENT
+
+inherit
+	LIBCURL_HTTP_CLIENT
+
+end

library/network/http_client/src/default/libcurl_or_net/default_http_client.e

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+note
+	description: "[
+			Default HTTP_CLIENT based on LIBCURL_HTTP_CLIENT.
+		]"
+	author: "$Author$"
+	date: "$Date$"
+	revision: "$Revision$"
+
+class
+	DEFAULT_HTTP_CLIENT
+
+inherit
+	HTTP_CLIENT
+
+feature -- Access
+
+	new_session (a_base_url: READABLE_STRING_8): HTTP_CLIENT_SESSION
+			-- Create a new session using `a_base_url'.
+		local
+			libcurl: LIBCURL_HTTP_CLIENT
+			net: NET_HTTP_CLIENT
+		do
+				--| For now, try libcurl first, and then net
+				--| the reason is the net implementation is still in progress.
+			create libcurl
+			Result := libcurl.new_session (a_base_url)
+			if not Result.is_available then
+				create net
+				Result := net.new_session (a_base_url)
+			end
+		end
+
+note
+	copyright: "2011-2015, Jocelyn Fiat, Javier Velilla, Eiffel Software and others"
+	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
+	source: "[
+			Eiffel Software
+			5949 Hollister Ave., Goleta, CA 93117 USA
+			Telephone 805-685-1006, Fax 805-685-6869
+			Website http://www.eiffel.com
+			Customer support http://support.eiffel.com
+		]"
+end

library/network/http_client/src/default/net/default_http_client.e

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+note
+	description: "[
+			Default HTTP_CLIENT based on NET_HTTP_CLIENT.
+		]"
+	author: "$Author$"
+	date: "$Date$"
+	revision: "$Revision$"
+
+class
+	DEFAULT_HTTP_CLIENT
+
+inherit
+	NET_HTTP_CLIENT
+
+end

library/network/http_client/src/default/null/default_http_client.e

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+note
+	description: "[
+			Default HTTP_CLIENT based on NULL_HTTP_CLIENT.
+		]"
+	author: "$Author$"
+	date: "$Date$"
+	revision: "$Revision$"
+
+class
+	DEFAULT_HTTP_CLIENT
+
+inherit
+	NULL_HTTP_CLIENT
+
+end