Resolve "Not initialise - save user's input only"

Closes #198 (closed) When a simple graph is loaded and no editing takes place then if it is saved nothing should change in the workflow.json. Some values that are boolean and define the functioning of the UI are being populated though. That only happens if a workflow is created without using ewoksweb and does not have for instance that the specific node is not a default_error_node. Then the json will include default_error_node: false since this is what will presented to the user.