BrooklynNode cluster + upgrade effector

Also effectors to:
  * select master in the cluster
  * set HA priority
  * set HA state
Declare a static class for this, rather than an anonymous inner class. Otherwise persisted state will get messed up: 1) adding your class could change the classnames of other existing classes with names like `EntityPredicates$1`; and 2) your classname would be brittle.