Bug #3, Tweaks to where and how configuration options are set and used

Hi Pablo,

As promised, here is a patch - do you want to add Elgg error handling in the try-catches?

* Includes an example `settings.php`
* Uses a try-catch - for exceptions raised for a missing/bad secret key
* TODO: as I don't know about Elgg error handling it uses a PHP "die()"


Relates to: [JuxtaLearn Cookie Authentication library](https://github.com/juxtalearn/juxtalearn-cookie-authentication).
* And, bug #3.

Thanks,


Nick