Refactor ReadDiagramEditor to make it more react-like

[calexh-sar]

Hopefully we can make this work in a more react way now that we know more. This would help us maintain and add to the component if we could get it working more as it should through react such as refreshing the diagram on state changes instead of navigating when needed.

This should also make it possible to NOT reload the whole page when clicking on the "View XML" button and instead just update the state like a normal react app.