the spark shell but with GraphX packages automatically imported
and with Kryo serialization enabled for GraphX types.
In addition the graphx-shell has a nifty new logo.
To make these changes minimally invasive in the SparkILoop.scala
I added some additional environment variables:
SPARK_BANNER_TEXT: If set this string is displayed instead
of the spark logo
SPARK_SHELL_INIT_BLOCK: if set this expression is evaluated in the
spark shell after the spark context is created.
