Inject variables in named maps in Automation context, instead of putting them at the root

Currently, all the variables value are injected in automation Context, directly at the "root". One side effect is that if a user names a global variable and a node variable the same way, one will override the over. It would be cleaner to inject two maps in the automation context: "WorkflowVariables" and "NodeVariables", and le the user be able to access it this way : WorkflowVariables['my_variable']="tutu";

This impacts also the code that outjects the variables values from context automation and update the values persisted on the node