Additional enhancements to VerticleManager

This is an extension to "Started cleaning up VerticleManager". That is, it relies on the previous pull request. 
On this request I kept the  commits separate as well. I coarsely squashed them though. I kept some separate to show how it evolved and thus hopefully makes its more easily comprehensible for you. But you should either apply all or none of them
All changes are related to Modules and module management

Juergen