More GUIDs

Most tables in our database have GUID fields, but we didn't use them very much, untill now. It is now possible to use GUIDs in itemlists, multieditors and more to define the template(s).

This is useful when installing premade templates, or importing and exporting your own templates between sites.

We have also updated the package designer and installer to always include the GUIDs as long as they exist.

<er:itemlist is also updated, and you can check the documentation here.