Implementation Process - ctree method

[antoinecarme]

for multi-class classification and regression (party package)

As described in issue #2

https://cran.r-project.org/web/packages/party/index.html
https://cran.r-project.org/web/packages/party/party.pdf
https://github.com/cran/party
https://github.com/topepo/caret/blob/master/models/files/ctree.R
https://github.com/topepo/caret/blob/master/models/files/ctree2.R

[antoinecarme]

Added yet another decision tree (ctree method) classification and regression models support