Bulk Operation

SPARK-18085 Move kvstore package to util.kvstore, add annotations

SPARK-18085 Remove stale applications from SHS listing

SPARK-18085 Speed up Stage page

SPARK-18085 In-memory key-value store implementation

SPARK-18085 Add controls for how much disk the SHS can use

SPARK-18085 Add auto-cleanup of old elements to the new app state store

SPARK-18085 Make SQL UI use new app state store

SPARK-18085 Speed up the new app state listener

SPARK-18085 Remove JobProgressListener (and other unneeded classes)

SPARK-18085 Simplify REST API class hierarchy

SPARK-18085 Make Jobs and Stages pages use the new app state store

SPARK-18085 Make the Storage page use new app state store

SPARK-18085 Make Executors page use new app state store

SPARK-18085 Make Environment page use new app state store

SPARK-18085 Hook up Spark UI to the new key-value store backend

SPARK-18085 Implement listener for saving application status data in key-value store

SPARK-18085 Use key-value store to keep History Server application listing

SPARK-18085 Key-value store abstraction and implementation for storing application data