Documenting SLA stats.

Bugs closed: AURORA-528

Reviewed at https://reviews.apache.org/r/22697/
Add test coverage for ResourceCounter.

Reviewed at https://reviews.apache.org/r/22942/
Database-backed implementation of QuotaStore.

Bugs closed: AURORA-421

Reviewed at https://reviews.apache.org/r/21459/
AURORA-231: Upgrade gradle license plugin to v9 which contains reduced debug output

Upgrades license plugin to latest version which contains updates to
silence ignored headers [1].

[1]: https://github.com/hierynomus/license-gradle-plugin/pull/31

Testing Done:
./gradlew -Pq clean build

Bugs closed: AURORA-231

Reviewed at https://reviews.apache.org/r/22956/
AURORA-552: License headers missing

Adds missing license headers

Bugs closed: AURORA-552

Reviewed at https://reviews.apache.org/r/22976/
Generate wrapper classes for all thrift structs in api.thrift.

Reviewed at https://reviews.apache.org/r/22998/
Fix build break in code generator.

Reviewed at https://reviews.apache.org/r/23087/
Fixing isort-check (no newline at the end) introduced by:
https://reviews.apache.org/r/22976/
Changing maintenance command to drain SLA-compliant hosts in a group.

Bugs closed: AURORA-542

Reviewed at https://reviews.apache.org/r/22842/
Use immutable types in AttributeStore.

Reviewed at https://reviews.apache.org/r/22999/
Revert "Returning a message when no tasks to kill."

Backing out of this change as there is no clean way to fix this now.

Bugs closed: AURORA-564

Reviewed at https://reviews.apache.org/r/23191/
Add a script that allows for easy selective rebuilding of components in the vagrant environment.

Reviewed at https://reviews.apache.org/r/22948/
Use java.util.Objects replacements for guava helpers.

Reviewed at https://reviews.apache.org/r/22982/
Export zero for racks that have no lost tasks.

Bugs closed: AURORA-548

Reviewed at https://reviews.apache.org/r/23189/
Add configuration plugins to default aurora client.

- Add a plugin to allow users to set logging levels.
- Add a plugin to allow users to configure whether or not unknown exceptions get
  caught or revealed.

Bugs closed: aurora-544, aurora-545

Reviewed at https://reviews.apache.org/r/22839/
Log loaded config file at level TRANSCRIPT (aka INFO+1)

Have client commands that load config files print the contents of the loaded config file to log at level TRANSCRIPT (aka INFO+1).

Bugs closed: aurora-567

Reviewed at https://reviews.apache.org/r/23199/
Fix TaskObserver for json endpoint usage.

Testing Done:
The `/j/task?task_id=id1,id2,...` endpoint now works.

Reviewed at https://reviews.apache.org/r/23211/
Move license header to inner node in angular fragments.

Bugs closed: AURORA-563

Reviewed at https://reviews.apache.org/r/23238/
Instruct quartz to use all daemon threads.

Bugs closed: AURORA-560

Reviewed at https://reviews.apache.org/r/23219/
Export a stat to track number of LOST gc_executors

Bugs closed: AURORA-562

Reviewed at https://reviews.apache.org/r/23180/