Several bug corrections and improvements

- added base system test capacle of bootin a drillbit cluster
- added a client sys test that submits a plan
- corrected a bug in ZKClusterCoordinator where endpoints would not get fetched before a cacheChanged event
- corrected a bug in HazelCache where it wouldn't support fetching an existing HazelCastInstance
- added a mini zookeeper cluster based on HBase's one but without the hadoop dependency
- made sure all tests pass