Variability: Improve "Adapt to Changes in Feature Model" intention

[kbirken]

In #1530, the "Update All Configurations" intention has been improved (performance, event handling, progress bar, ...). The intention propagateFMchangesToConfig for updating a single configuration should be improved in a similar way.

Implementation hint: The implementation of the single intention should probably use the same class as the "Update all configs" intention (class UpdateAllConfigsTask).