[SPARK-1853] Show Streaming application code context (file, line number) in Spark Stages UI

This is a refactored version of the original PR https://github.com/apache/spark/pull/1723 my @mubarak

Please take a look @andrewor14, @mubarak

Could this be named `coreCallSiteFilterFunc` since it relates specifically to spark core? This conveys more information than "default".