removed mllib/src/test/java/org/apache/spark/mllib/tree/JavaDecisionTreeSuite.java since it fails currently

Comments which should have been added to previous commit:

Fixed one test in DecisionTreeSuite to undo a change in previous commit (“stump with categorical variables for multiclass classification”).  Reverted impurity from Entropy back to Gini.

Java compatibility:
* Changed non-static train() methods’ names to run() to avoid conflicts with static train() methods in Java.
* Added setter functions to *Params classes.
Merge branch 'decisiontree-api' of github.com:jkbradley/spark into decisiontree-api