previous evaluators checking back in for driver HA
update recovery logic based on working 2.4.1 jar
add retained container in a more natural way and remove the need to add EvaluatorManager based on recovery heartbeat
add driver restart runningtask and activecontext handler
merge with master
add EvaluatorsChangeLog to HDFS, trigger failedEval when eval failed during driver restart, remove dependency on local file
close hdfs reader once done
Merge remote-tracking branch 'origin' into yingdac-evaluators-checking-back-in

Conflicts:
	reef-common/src/main/java/com/microsoft/reef/runtime/common/driver/evaluator/EvaluatorManager.java
Merge branch 'master' of https://github.com/Microsoft-CISL/REEF into yingdac-evaluators-checking-back-in
Minor updates
remove all static fields in evaluatormanager
fix other CR comments
minor change in comment to trigger build
Merge branch 'master' of https://github.com/Microsoft-CISL/REEF into yingdac-evaluators-checking-back-in
State checks for `DriverStatusManager`
State checks for `DriverStatusManager`
Code pass through EvaluatorManager
Merge pull request #946 from Microsoft-CISL/yingdac-evaluators-checking-back-in

previous evaluators checking back in for driver HA