Switch config loaders to DOM API

All four config loaders end up translating the parsed structure to Binding form only to feed it into DataBroker.

This is completely unnecessary, as the data is coming from XML files and is therefore in DOM form – hence we end up encoding it to and from Binding for no particularly good reason.

We are also using inefficient datastore operations in individual implementations, which really should be using the bare minimum required.

Switching to DOM interfaces is a bit of juggling of paths, but will improve performance and most notably will make config loaders independent of codec services.