Initial commit of WIP PR for terasort benchmark.

As discussed on list, this is a WIP for Spark Terasort.
just copy [hadoop TeraScheduler](https://github.com/apache/hadoop/blob/trunk/hadoop-mapreduce-project/hadoop-mapreduce-examples/src/main/java/org/apache/hadoop/examples/terasort/TeraScheduler.java) and change the package name from `package org.apache.hadoop.examples.terasort;` to `package org.apache.spark.examples.terasort;`