Started cleaning up VerticleManager

VerticleManager class comment states the requirement that it needs some cleanup. And I think that is very true. I started by
-  introducing the ModuleRepository interface
- "copying" the respective code from VerticleManager into DefaultModuleRepository
- allowed to register multiple repositories with VerticleManager (improvement)
- introduced Unzipper (re-usable by different repositoriy) and moved the code from VerticleManager
- introduced ModuleConfig and moved the code from VerticleManager

Fixed an issue with BlockingAction and its handlers. It can be provided via the constructor or subclassed and behavior is now more consistent

I grouped the commits in a way, that they are more easily reviewable.

Juergen