Use ScenarioRunner rather than ScenarioDesigner

[martinmaher]

Citrus's TestDesigner will be eventually removed from Citrus. As a result the ScenarioDesigner will have to be removed too. To avoid future migration problems it would be better to deprecate this class now and remove it completely in one of the next releases.

What has to be done:

• Use the ScenarioRunner in the sample projects
• Deprecate the ScenarioDesigner class
• Update the documentation: replace all ScenarioDesigner references with ScenarioRunner