CRASH-189 : Use command script return value only when it is explictly returned
Improve propagation of flush/close in the pipeline
Minor cleanup
Move the CommandCreationException to the spi package
Avoid to use inner class that carry a lot of complexity
Refactor stuff a bit to simplify
- rename LoggerRenderable -> LoggerRenderer
- have MemoryUsageLineRenderer to be package protected
Improve developer documentation