Restructure image target node

[jaapio]

Feature request

In #914 the image target was added, but rather than adding a new node to the image as target it would make more sense to wrap the image node in a link node like a decoration on the image node.

To do this we need to change the hyperlink nodes to a compound version that will allow us to make a more complex node structure. We consider this a BC break as template authors need to update their templates. Therefor this has been scheduled for v2.0.0 of this library.