Moved web_server tutorials

Author: javiereguiluz

redirection_map

@@ -236,4 +236,5 @@
 /cookbook/upgrade/patch_version /upgrade/bundles
 /cookbook/validation/custom_constraint /validation/custom_constraint
 /cookbook/validation/group_service_resolver /validation/group_service_resolver
-/cookbook/validation/severity /validation/severity
+/cookbook/validation/severity /validation/severity
+/cookbook/web_server/built_in /web_server/built_in