add performance tests for pyspark

copied from spark tests
Added and tested MLlib performance tests
EventLogging enabled to better diagnose failed tests
Reformatted code, fixed issues
SBT version updated
Two minor changes to PySpark tests:

- Don’t specify master when creating SparkContext; this allows us to use
  the right master when running the program via spark-submit.
- Comment out the Python tests in config.py.template
  (the default template runs no tests)
Added Logistic Regression with L-BFGS
Merge with pull request
Final changes before merge