Place OK and Logging controller helpers outside of controller itself

[raymens]

By placing these lines outside of the controller they can be re-used in other controllers.

https://github.com/swlaschin/Railway-Oriented-Programming-Example/blob/master/src/FsRopExample/Controllers.fs#L138-L177

[swlaschin]

That's a good suggestion. I'll put them in the helper module. Thanks!