Improve aurora command-line help using metavars.

Bugs closed: aurora-737

Reviewed at https://reviews.apache.org/r/25918/
AURORA-736 - Update committer docs with steps for adding a gpg key

Bugs closed: AURORA-736

Reviewed at https://reviews.apache.org/r/25898/
Allow optional initial and desired states.

Bugs closed: AURORA-741

Reviewed at https://reviews.apache.org/r/25953/
Remove about plugin.

Reviewed at https://reviews.apache.org/r/25955/
Enable beta updater in example cluster.

Reviewed at https://reviews.apache.org/r/25958/
Calculate median SLA stats over sampling interval.

Bugs closed: AURORA-733

Reviewed at https://reviews.apache.org/r/26002/
Implementing quota checking for async job updates.

Bugs closed: AURORA-686

Reviewed at https://reviews.apache.org/r/25812/
Expose in progress and recently completed updates in UI

Bugs closed: AURORA-745

Reviewed at https://reviews.apache.org/r/25963/
When creating an update, store only the delta between the initial and desired states.

Bugs closed: AURORA-718

Reviewed at https://reviews.apache.org/r/25969/
Fix extra constructor arg causing build break.

Reviewed at https://reviews.apache.org/r/26024/
Skip past irrelevant jobs when running cron show command.

Bugs closed: AURORA-753

Reviewed at https://reviews.apache.org/r/26015/
Fix checkstyle broken by rb/26015.

Testing Done:
My commit made it in.

Reviewed at https://reviews.apache.org/r/26043/
Adding support for transient storage errors.

Bugs closed: AURORA-187

Reviewed at https://reviews.apache.org/r/25970/
Run python style checks in jenkins.

Reviewed at https://reviews.apache.org/r/26044/
Fix breadcrumb and page titles in UI.

Reviewed at https://reviews.apache.org/r/26048/
Use BufferedOutputStream for deflater

Testing Done:
./gradlew build

Microbenchmark with a scheduler backup from my production environment.

Before:
# Deflater.DEFAULT_COMPRESSION
# (No BufferedOutputStream)
# DeflaterOutputStream(512B)
deflate: 16664ms
total:17219ms
compression ratio: 647270930/92690409 = 698.31%

After:
# Deflater.DEFAULT_COMPRESSION
# BufferedOutputStream(256KiB)
# DeflaterOutputStream(256KiB)
deflate: 11807ms (4857ms speedup)
total: 12379ms (4840ms speedup)
compression ratio: 647270930/92690409 = 698.31% (0% improvement)

Bugs closed: AURORA-722

Reviewed at https://reviews.apache.org/r/26012/
Renaming update to beta-update in client v2

Bugs closed: AURORA-757

Reviewed at https://reviews.apache.org/r/26089/
Adding JobUpdateRequest validation.

Bugs closed: AURORA-649

Reviewed at https://reviews.apache.org/r/25481/
Revert "Run python style checks in jenkins."

Reviewed at https://reviews.apache.org/r/26093/
Add updater support for disabling rollback and batched update settings.

Bugs closed: AURORA-744, AURORA-747

Reviewed at https://reviews.apache.org/r/26106/