Make the offer hold jitter window configurable.

Bugs closed: AURORA-313

Reviewed at https://reviews.apache.org/r/25398/
Make "aurora job status" JSON output more friendly.

Use string names instead of numeric values for ScheduleStatus fields of
records rendered in JSON.

Bugs closed: aurora-666

Reviewed at https://reviews.apache.org/r/25505/
Apply GzipFilter to POSTs as well as GETs

Bugs closed: AURORA-697

Reviewed at https://reviews.apache.org/r/25548/
Add information about log initialisation step.

Reviewed at https://reviews.apache.org/r/25391/
Show reason for PENDING state in Scheduler UI

Bugs closed: AURORA-495

Reviewed at https://reviews.apache.org/r/25552/
Dropping synchronized from validateIfLocked()

Bugs closed: AURORA-702

Reviewed at https://reviews.apache.org/r/25556/
Set principal field in FrameworkInfo struct.
Enable framework auth in Vagrant.