Need to update the Guide

[YvesS]

The Developer Guide pages (http://okapiframework.org/devguide/) are very much outdated. With more and more developers using the framework we need to update them.

There is a warning about the fact they are partially outdated in the index page, but not for each page.

Ideally the guide should be part of the Javadoc pages.

[YvesS]

The source for the developer guide pages is in \website\devguide