Decision Tree: Performance Improvement on Tree Growing Engine
Decision Tree: Performance Improvement on Tree Growing Engine

Jira: MADLIB-607

This file implements the tree growing engine for C4.5 and RF, which includes
training, classification, scoring and displaying.  There are few changes on
classification/scoring/displaying/cleaning.  Most of changes are in training
process.

The steps of training:
0. Encoding the training table.
1. Generating ACC (a group by statement).
2. Generating ACS and calculating SCVs and finding the best SCVs (in a single
SQL statement).
3. creating the child nodes (a sigle SQL statement).
4. Iterate the step 1 to step 3 until we met the stop condition.

orhankislal/incubator-madlib,apache/incubator-madlib,orhankislal/incubator-madlib,cooper-sloan/incubator-madlib,madlib/madlib,rvs/incubator-madlib,orhankislal/incubator-madlib,njayaram2/madlib,apache/incubator-madlib,lmatthieu/incubator-madlib,njayaram2/incubator-madlib,cooper-sloan/incubator-madlib,cooper-sloan/incubator-madlib,mktal/incubator-madlib,iyerr3/incubator-madlib,hpandeycodeit/incubator-madlib,njayaram2/incubator-madlib,njayaram2/madlib,njayaram2/incubator-madlib,lmatthieu/incubator-madlib,cooper-sloan/incubator-madlib,mktal/incubator-madlib,iyerr3/incubator-madlib,rashmi815/incubator-madlib,orhankislal/madlib,iyerr3/incubator-madlib,rvs/incubator-madlib,njayaram2/madlib,orhankislal/madlib,njayaram2/incubator-madlib,hpandeycodeit/incubator-madlib,orhankislal/madlib,njayaram2/incubator-madlib,hpandeycodeit/incubator-madlib,lmatthieu/incubator-madlib,orhankislal/incubator-madlib,rvs/incubator-madlib,rashmi815/incubator-madlib,mktal/incubator-madlib,mktal/incubator-madlib,mktal/incubator-madlib,apache/incubator-madlib,rashmi815/incubator-madlib,madlib/madlib,rashmi815/incubator-madlib,cooper-sloan/incubator-madlib,iyerr3/incubator-madlib,njayaram2/madlib,rvs/incubator-madlib,lmatthieu/incubator-madlib,madlib/madlib,rashmi815/incubator-madlib,orhankislal/incubator-madlib,apache/incubator-madlib,rvs/incubator-madlib,orhankislal/madlib,iyerr3/incubator-madlib,orhankislal/madlib,njayaram2/madlib,hpandeycodeit/incubator-madlib,madlib/madlib,madlib/madlib,hpandeycodeit/incubator-madlib,lmatthieu/incubator-madlib,apache/incubator-madlib