SCHEMA-436. Table layout updates must push notifications to ZooKeeper

 - Introduce HBaseTableLayoutUpdater that should eventually handle all
   of the table layout updating process.
 - Minimally plug the layout updater into HBaseKiji.modifyTableLayout()
 - Adds an integration that validates HBaseKiji.modifyTableLayout().

issue: https://jira.kiji.org/browse/SCHEMA-436
review: https://review.kiji.org/r/888