Updated Documentation to include wysiwyg config options.

I saw that you can actually customize the wysiwyg editor, which is a great feature, but did not find any documentation for it.

I don't really know how I can build all this code to make sure I didn't create any error, so if you could go over it quickly or just let me now how I can build the docs so I can check myself that would be great. Also I don't really know what the `wysiwyg additional options` do, hence the description is a bit vague. Maybe we could improve that and give an example or link to somewhere in the tinymce documentation.