Enhance HttpScenarioGenerator to use the OpenAPI Connector for random message generation

[tschlat]

Citrus Simulator has the HttpScenarioGenerator, which generates scenarios for operations of a Swagger Spec (OpenAPI 2.0). Citrus now provides an OpenAPI connector, that supports OpenAPI 2.0 and OpenAPI 3.0. Consequently, the HttpScenarioGenerator should use this connector and provide scenarios for both Versions.