TaskStatus: Fix javadocs
Introduce TaskExistsException, thrown by TaskStorage.insert when appropriate
TaskToolbox: Replace IndexerCoordinatorConfig with TaskConfig
TaskStorageQueryAdapter: Rename some methods and tweak javadocs for clarity
TaskGroup: Add javadocs
TaskQueue: Clarify "Naptime!" log message
TaskQueue: Tweak to implementation of findTaskGroupForTask
TaskConsumer: Commit to segment db in one transaction