Allow undeclared variables for workflows

Current Situation

• The JOC Cockpit requires variables to be declared with the workflow.
• Orders specify variables only that are declared with the workflow.

Desired Behavior

• A global "allow_undeclared_variables" setting is made available from the Settings view. Default value: false.
• If the global setting holds the value "true" then
  • JOC Cockpit offers the checkbox "Allow undeclared variables" for workflows.
  • users specify per workflow if they allow undeclared variables. Default value: false.
  • if the workflow allows undeclared variables users can specify undeclared variables 
    • with a schedule
    • when adding orders from the Workflows view
    • when modifying orders from the Daily Plan view and the OrdersOverview view.