Adding authz check into descheduleCronJob RPC.

Bugs closed: AURORA-566

Reviewed at https://reviews.apache.org/r/26283/
Add a doc about dedicated hosts.

Bugs closed: AURORA-703

Reviewed at https://reviews.apache.org/r/26244/
Fix checkstyle and add checkstyle back to jenkins.

Testing Done:
build.sh

Reviewed at https://reviews.apache.org/r/26098/
Remove "UI" from page titles.

Reviewed at https://reviews.apache.org/r/26269/
Implementing update history pruner.

Bugs closed: AURORA-743

Reviewed at https://reviews.apache.org/r/26232/
Make thermos more cognizant of user deletions

This is changes 1 of 2 for AURORA-175.  The second change adds an exit
status contract between Aurora and Thermos.

This change allows a process in the Thermos state machine to go directly
from WAITING -> FAILED if the user associated with that process has been
deleted.  It also persists a 'uid' field to the Thermos RunnerHeader so that
we can check against process UIDs which in theory have higher fidelity than
usernames.

Bugs closed: AURORA-175

Reviewed at https://reviews.apache.org/r/25972/
Prevent initial ZK timeouts from killing the executor.

In addition, prevent uncaught exceptions from killing the executor.
Kevin's feedback.
Bill's Feedback.
Kevin's Feedback.
Brian's Feedback.
Split client creation and serverset generation.
WIP
WIP WIP WIP
WIP.
WIP
WIP.
WIP
Remove unused import.
Add test.