Added Hazelcast support
Slimmer main() method with default choice of app to run
Fix default sources to empty
Added embedded ZK server; picking random port for sshd
Slight change to javadoc; candidate impl
Renamed renounce to yield
Ensure that ZK leaders that yield can become leaders again
Removed role and id from Context
Minor SimpleCandidate refactoring

SimpleCandidate exposes a public yieldLeadership method instead of
exposing its leader Context.
Handle uncaught exceptions from onGranted
Tidy up POM XML (using tabs consistently)