Add spark.executor.memory to differentiate executor memory from spark-shell

RDDInfo available from SparkContext

Once we find a split with no block, we don't have to look for more.

Fix createActorSystem not actually using the systemName parameter.

Tests for DAGScheduler

Conflicts:
	core/src/main/scala/spark/scheduler/DAGScheduler.scala

This meant all system names were "spark", which worked, but didn't
lead to the most intuitive log output.

This fixes createActorSystem to use the passed system name, and
refactors Master/Worker to encapsulate their system/actor names
instead of having the clients guess at them.

Note that the driver system name, "spark", is left as is, and is
still repeated a few times, but that seems like a separate issue.

Reduce the amount of duplicate logging Akka does to stdout.

Given we have Akka logging go through SLF4j to log4j, we don't need
all the extra noise of Akka's stdout logger that is supposedly only
used during Akka init time but seems to continue logging lots of
noisy network events that we either don't care about or are in the
log4j logs anyway.

See:

http://doc.akka.io/docs/akka/2.0/general/configuration.html

    # Log level for the very basic logger activated during AkkaApplication startup
    # Options: ERROR, WARNING, INFO, DEBUG
    # stdout-loglevel = "WARNING"

These operations used to wait for all the results to be available in an
array on the driver program before merging them. They now merge values
incrementally as they arrive.

Add more private declarations.

Stop BlockManagers metadataCleaner.

Use spark.local.dir for PySpark temp files (SPARK-580).

Do not launch JavaGateways on workers (SPARK-674).

The problem was that the gateway was being initialized whenever the
pyspark.context module was loaded.  The fix uses lazy initialization
that occurs only when SparkContext instances are actually constructed.

I also made the gateway and jvm variables private.

This change results in ~3-4x performance improvement when running the
PySpark unit tests.

Changed PartitionPruningRDD's split to make sure it returns the correct split index.

Fix stdout redirection in PySpark.

SPARK-673: Capture and re-throw Python exceptions

Remove activation of profiles by default

This patch alters the Python <-> executor protocol to pass on
exception data when they occur in user Python code.