Make some of the front-end logic less complicated

[frostyfan109]

The first step has already been completed, that being making configureMessage and translateGraph work for both the schema view and the graph view. Similar to this situation, there's a lot of logic scattered throughout the application that is bug prone and unsustainable.

• Things like how every modal has its own state property regulating whether its rendered or not, meaning that programatically displaying a modal (such as the error page which is not user input) involves making sure that you hide every other modal. If one adds a modal at the moment and forgets this small detail, it adds another bug.
• The selectedNode state property getting way too complicated and probably needs to be completely redone.
  • The split pane for the object viewer is a headache because if anything modifies the selectedNode property, they have to ensure that _updateDimensions is called or it will cause a bug.
  • Every tool that uses it should probably have its own unique selectedNode and it should only get programmatically wiped in places such as when the schema/graph view gets toggled and the node/link will never exist again.
• There are probably other things that I'm forgetting.

[frostyfan109]

The disaster that selectedNode has turned into has been sorted out. The split pane has also been sorted out.