Shows task status and running tasks on Stage Page: fixes SPARK-804 and 811
Changed ifs with returns to if/else
Removed finished status for task info, changed name of success case
Fixed consistency of "success" status string
Fix setting of SPARK_EXAMPLES_JAR
Merge pull request #729 from karenfeng/ui-811

Stage Page updates
Merge pull request #728 from jey/examples-jar-env

Fix setting of SPARK_EXAMPLES_JAR