Design and implement sensibe non-elementPath dependent API for getting attribute values

A crude solution would be getters for DataInputs, but since DataInput can map to multiple properties and each may interpret the value differently, this is probably not enough. We likely need some kind of "alias" element for either directly exposing individual properties of elements or whole elements themselves. If the whole element is exposed, it would be nice to dynamically map the properties of the element to Qt properties of the corresponding QObject in the API.