initial commit: TajoMaster HA Manager utilizing HDFS Cluster.
Adding HA elector to client side.
Rename HAManager to HAService
Rename HAManager to HAService (adding missing file)
Rename HAUtil to HAServiceUtil
Update HA status to web interface.
Adding active master elector to TajoCli and QueryExecutorServlet.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-704
Fixed various client bugs.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-704
Adding auto failover for running queries.
Adding current active master address to backup master.
Remove unread field.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-704

Conflicts:
	tajo-client/src/main/java/org/apache/tajo/cli/TajoCli.java
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-704
Merge branch 'master' of https://github.com/blrunner/tajo into TAJO-704
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-704
Fixed NPE in the web UI.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-704
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-704

Conflicts:
	tajo-core/src/main/java/org/apache/tajo/webapp/QueryExecutorServlet.java