Update vagrant provisioning and aurorabuild scripts to remove the need to sudo to run build
commands in the vagrant image.

Bugs closed: AURORA-688

Reviewed at https://reviews.apache.org/r/25361/
Update slave url to use the thermos port.

Bugs closed: AURORA-644

Reviewed at https://reviews.apache.org/r/25365/
Refactoring SchedulerCore final part.

Bugs closed: AURORA-94

Reviewed at https://reviews.apache.org/r/24815/
Tweak contributors doc to add details on finding newbie issues.

Reviewed at https://reviews.apache.org/r/25319/
Adding support for per-job task status metrics.

Bugs closed: AURORA-685

Reviewed at https://reviews.apache.org/r/25357/
Adding initial GC task delay on scheduler restart.

Bugs closed: AURORA-608

Reviewed at https://reviews.apache.org/r/24915/