Make cluster manager pluggable so Vert.x core now no longer has any dependency on Hazelcast. This allows you to write your own cluster manager implementations using a different cluster provider. Also implemented high availability (HA) which includes failover of modules from one node to another and includes quorums.
prevent NPE if context is used during shutdown
some fixes to get hatests running on CI
Merge branch 'master' into feature/config-in-verticlefactory