Import should use the workflowNames array of a schedule instead of the workflowName property

Current Situation

Due to changes in the schedule schema (1.3.0) the property workflowName is not updated anymore. Instead, starting with JS7 2.3.0, an array of workflow names is used with the property name workflowNames.
This results in a NPE on importing newer schedules.

Desired Behavior

The import of schedules should work with both versions of the schedule schemas, before 1.3.0 and after 1.3.0.