Revert "Preserving sandbox deleted task history (part 2: state machine)."

Reason: Needs to support rollback scenario.

This reverts commit 359d0fb4885d100b44f5e5fa68cf69eb562577af.
Remove the failed JobManager abstraction.

This removes a circular dependency between CronJobManager and SchedulerCoreImpl.

Reviewed at https://reviews.apache.org/r/19808/
AURORA-29: Clean up resource files under src/resources/org/apache/

Bugs closed: AURORA-29

Reviewed at https://reviews.apache.org/r/19819/
Optional is printed in scheduler thrift response message