Add method overloads to be friendlier with questions and actions returning Task

[Galad]

Some methods across the application do not play nice with asynchronous programming.
For instance the Then method takes an Action<T> to assert the result. With asynchronous programming, the consumer receives a Task, which he needs to await before making the assertion. This is unnecessary and could be done by the Then method itself.

• Add Then overload or extension method that awaits the result of Task<T> and pass it to the assertion action
• Add Select overload that unwrap the value from the task
• Add SelectMany overload that unwrap the value from the task
• CompositeAction that execute asynchronous actions sequentially

[Galad]

The interface IVerifies will changed in order to support async properly