Cross-Origin Resource Sharing initial support

Initial support for the Cross-Origin Resource Sharing specification.
This allows JavaScript to make requests across domain boundaries.

Also reviewed the filter example to get rid of the context and
the generic classes (we can actually use {WSF_REQUEST}.execution_variable
and {WSF_REQUEST}.set_execution_variable).

Links:
* How to enable server-side: http://enable-cors.org/server.html
* Specification: http://www.w3.org/TR/cors/
* Github: http://developer.github.com/v3/#cross-origin-resource-sharing

library/server/wsf/router/filter/wsf_cors_filter.e

@@ -0,0 +1,33 @@
+note
+	description: "Cross-Origin Resource Sharing filter."
+	author: "Olivier Ligot"
+	date: "$Date$"
+	revision: "$Revision$"
+	EIS: "name=Cross-Origin Resource Sharing", "src=http://www.w3.org/TR/cors/", "tag=W3C"
+
+class
+	WSF_CORS_FILTER
+
+inherit
+	WSF_FILTER
+
+feature -- Basic operations
+
+	execute (req: WSF_REQUEST; res: WSF_RESPONSE)
+			-- Execute the filter.
+		do
+			res.header.put_access_control_allow_all_origin
+			execute_next (req, res)
+		end
+
+note
+	copyright: "2011-2013, Jocelyn Fiat, Javier Velilla, Olivier Ligot, 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/server/wsf/router/filter/wsf_cors_options_filter.e

@@ -0,0 +1,59 @@
+note
+	description: "Filter that handles an OPTIONS request, with Cross-Origin Resource Sharing support."
+	author: "Olvier Ligot"
+	date: "$Date$"
+	revision: "$Revision$"
+	EIS: "name=Cross-Origin Resource Sharing", "src=http://www.w3.org/TR/cors/", "tag=W3C"
+
+class
+	WSF_CORS_OPTIONS_FILTER
+
+inherit
+	WSF_FILTER
+
+	WSF_URI_TEMPLATE_HANDLER
+
+create
+	make
+
+feature {NONE} -- Initialization
+
+	make (a_router: like router)
+			-- Initialize Current with `a_router'.
+		do
+			router := a_router
+		ensure
+			router_set: router = a_router
+		end
+
+feature -- Access
+
+	router: WSF_ROUTER
+			-- Associated router
+
+feature -- Basic operations
+
+	execute (req: WSF_REQUEST; res: WSF_RESPONSE)
+			-- Execute the filter.
+		local
+			msg: WSF_CORS_OPTIONS_RESPONSE
+		do
+			if req.is_request_method ({HTTP_REQUEST_METHODS}.method_options) then
+				create msg.make (req, router)
+				res.send (msg)
+			else
+				execute_next (req, res)
+			end
+		end
+
+note
+	copyright: "2011-2013, Jocelyn Fiat, Javier Velilla, Olivier Ligot, 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