Give more detailed instructions in script/rails in engine

closes #4894

railties/lib/rails/engine/commands.rb

@@ -34,6 +34,10 @@
  destroy     Undo code generated with "generate" (short-cut alias: "d")
 
 All commands can be run with -h for more information.
+
+If you want to run any commands that need to be run in context
+of the application, like `rails server` or `rails console`,
+you should do it from application's directory (typically test/dummy).
   EOT
   exit(1)
 end