[SPARK-2309][MLlib] Multinomial Logistic Regression

#1379 is automatically closed by asfgit, and github can not reopen it once it's closed, so this will be the new PR.

Binary Logistic Regression can be extended to Multinomial Logistic Regression by running K-1 independent binary logistic regression models. The following formula is implemented. 
http://www.slideshare.net/dbtsai/2014-0620-mlor-36132297/25