Support manual lifecycle management of ContainerEngine

[npepinpe]

Is your feature request related to a problem? Please describe.

There are some cases where we may want to modify the engine or container before starting it. In such cases, it should be possible to manually control the lifecycle of the ContainerEngine instance in a streamlined manner. Right now, you have to call all the initialization methods manually, which imply knowledge of the implementation.

Describe the solution you'd like

Doing a simple engine.start() takes care of the initialization, whether used via the junit extension or not. Similarly, engine.stop() takes care of resetting everything.