apache-spark 0.9.0 (new formula)

Creates the assembly for Apache Spark at https://spark.incubator.apache.org/
Building the project from source.
Name against the convention "apache-spark" because spark formula already
exists.
Currently will build with defaults against Hadoop 1.x

Room for improvements:
- add dependency on Mac OS X java
- add build config options
- provide more shell scripts to /usr/local/bin (however not all of them are required and they are in 'libexec')