Fixed DefaultOrchestrator's log appender.

DefaultOrchestrator's log appender now appends logs for all the major components of Orchestrator: itself, instance monitor, git file monitor, minion controller, and config transitioner.
Fixed DefaultOrchestrator's config logic.

Both running config and target config are now updated within the tryTransition() method.
minionsController -> minionController in DefaultOrchestrator + minor comments.
Fixed logs of ZooKeeperInstanceMonitor.

In particular, listeners should be notified after the log message.
Fixed ConfigTransitioner: instances -> endpoints.

ConfigTransitioner does not deal with Instance objects, only with strings representing endpoints.
Updated Instance.toString().
Renamed "running config" to "active config".