Decision Tree: Fix scoring API failure caused by the wrong encoding result.
Decision Tree: Fix scoring API failure caused by the wrong encoding result.

Jira: MADLIB-632

During encoding, we should not btrim the attribute value, since we will use it
as join key between encoded table and raw training table.  The second problem
was we always used 'explict' option during encoding in classification/scoring.
We should have used the passed parameter.

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