requirementsascode v0.3.0

Pre-release of requirementsascode, with the following features:

• Document a use case model, actors, use cases, use case flows, use case steps, events
• Run the use case model for a particular actor
• Specify cross-cutting concerns, e.g. measuring performance.

Limitations include:

• No support for included use cases or subflows so far

What's new:

• requirementsascodecore: introduce TestUseCaseRunner for simple testing of flows
• shoppingappjavafx: extended example by additional steps

API changes:

• Cross-cutting concerns: method UseCaseRunner.adaptSystemReaction replaces one-arg constructor of UseCaseRunner
• UseCaseStep.reactWhile replaces UseCaseStep.repeatWhile (because it's not a loop, it just may react to the same event several times)
• .continueAfter and .restarts can now be used anywhere .system is used, and only there (to make the API more consistent and easy to use)