Implement help for v2 bridge

Implement help message generation for the noun/verb framework.

Bugs closed: aurora-203

Reviewed at https://reviews.apache.org/r/18267/
AURORA-186: rename ThermosExecutor to AuroraExecutor, clean up thermos-isms from ExecutorBase

split all thermos-specific stuff out of thermos_executor.py

Testing Done:

this adds executor-small and executor-large, the latter of which runs the
executor tests.

Both ./pants src/test/python/apache/aurora/executor:executor-large and e2e
passes locally for me.

Bugs closed: AURORA-186

Reviewed at https://reviews.apache.org/r/18239/
Adding admin_client sla_list_safe_domain command.

Bugs closed: AURORA-208

Reviewed at https://reviews.apache.org/r/18296/
Renamed getJobSummary call to getRoleSummary

getJobSummary will be reused to return the jobs.

Testing Done:
gradle clean build
gradle run and tested on my laptop

Bugs closed: AURORA-64

Reviewed at https://reviews.apache.org/r/18340/
Prepare and launch GC executor tasks asynchronously.

Bugs closed: AURORA-214

Reviewed at https://reviews.apache.org/r/18141/
Updated FakeSchedulerDriver to work with delayed driver registration semantics of SchedulerLifeCycle.

Updated FakeSchedulerDriver to register scheduler on start instead of run.

Testing Done:
gradle clean build.
rm /tmp/testing_log_file && gradle run

Bugs closed: AURORA-179

Reviewed at https://reviews.apache.org/r/18300/
Add a packaging target for clientv2.

Bugs closed: aurora-226

Reviewed at https://reviews.apache.org/r/18354/
Aurora-193: fix license plugin

Adds the license header plugin and sets the correct source sets.

Replaces patch in review: https://reviews.apache.org/r/17771/

Testing Done:
All tests passed locally with rm -rf .gradle && ./build-support/jenkins/build.sh

Bugs closed: AURORA-193

Reviewed at https://reviews.apache.org/r/18316/
Adding aurora_admin sla_probe_hosts command.

Bugs closed: AURORA-209

Reviewed at https://reviews.apache.org/r/18440/
Reworked LogStorage to avoid unnecessary extra calls to write().

Bugs closed: AURORA-134

Reviewed at https://reviews.apache.org/r/18241/
AURORA-225: Shell scripts in checkout should use an absolute path

Testing Done:
Submitted this review with the following command:
 ../rbt post -o -g (from inside of build-support directory)

Bugs closed: AURORA-225

Reviewed at https://reviews.apache.org/r/18345/
Upgrade pex to twitter.common.python==0.3.1

Testing Done:
Tested upgrade on clean and dirty master.

Reviewed at https://reviews.apache.org/r/18481/
Accumulate read/write timing in MemStorage for top-level operations only.

Bugs closed: AURORA-135

Reviewed at https://reviews.apache.org/r/18240/
Improving sla_list_safe_domain performance

Bugs closed: AURORA-233

Reviewed at https://reviews.apache.org/r/18485/
Generate cron predictions using -Duser.timezone=GMT.

Test data was generated with a system timezone of PST - regenerate
it with GMT.

Testing Done: Manual testing against internal implementation - test
against quartz coming in a later review.

Bugs closed: AURORA-132

Reviewed at https://reviews.apache.org/r/18490/
AURORA-200: set_quota should die if given invalid arguments

Bugs closed: AURORA-200

Reviewed at https://reviews.apache.org/r/17877/
Remove rogue apostrophes.

Reviewed at https://reviews.apache.org/r/18523/
Make markdown TOC and anchors more plaintext-friendly.

Reviewed at https://reviews.apache.org/r/18528/
Updated test to use environment variable if it exits.

Testing Done:
./build-support/jenkins/build.sh runs successfully

Bugs closed: AURORA-101

Reviewed at https://reviews.apache.org/r/18598/
Make http signaler timeout secs configurable via environment variable.

This is a band-aid for the issue described in AURORA-224. Further
improvements would be made possible by refactoring the updater
to completely remove client-side health checking (delegating to
thermos, which already supports a much richer system of delegated
health checks).

Testing Done:
./build-support/jenkins/build.sh

Bugs closed: AURORA-224

Reviewed at https://reviews.apache.org/r/18602/