SENTRY-74: Add column-level privileges for Hive/Impala (Dapeng Sun and Xiaomeng Huang via Prasad Mujumdar)
SENTRY-456-Service-discovery-for-SENTRY-high-availab
SENTRY-463-Refactor-SentryServiceClientFactory-chang
SENTRY-464-Add-HASentryPolicyServiceClientImpl-for-h
SENTRY-459-Security-mode-Kerberos-support-for-SENTRY