[SPARK-707] Adding Java versions of Pi, LogQuery and K-Means examples

Add foldByKey

CoalescedRDD for many partitions

Remove try/catch block that can't be hit.

call setConf from input format if it is Configurable

CoalescedRDD changed to work with a big number of partitions both in the original and the new coalesced RDD.
The limitation was in the range that Scala.Int can represent.

Add PairRDDFunctions.subtractByKey.

Fix local metrics

Add a log4j compile dependency to fix build in IntelliJ

Also rename parent project to spark-parent (otherwise it shows up as
"parent" in IntelliJ, which is very confusing).

Close the reader in HadoopRDD as soon as iteration end.

Fix broken link to YARN documentation

Fix broken link in Quick Start

Send block sizes as longs in BlockManager updates