Verticle manager (final)

This is the final (and most comprehensive) of 3 pull requests on the topic of VerticleManager improvements. It's a separate topic branch derived from the previous ones (thus github showing them in the commit list).

When reviewing it, it's probably best to checkout  all of the commits, as some commits in between only represent interim stages with details that might have changed again in a later commit.  I kept the commits as usual, for you to more easily follow the line of thoughts.

When reviewing it's probably best to start with VerticleManager and go from there.

It's rebased on the lasted master and passes all tests on Ubuntu and Windows, but likely needs some more testing as I have my doubts that existing tests really cover all functionalities. E.g. preserve-cwd. Would be nice if someone would contribute that.

Feel free to ask questions. Any feedback is welcome.

Juergen