GitLab

* added argument eval_train_metric

* remove unnecessary whitespace

* removed further trailing whitespace

* move new argument to the last position

* update R docu

* unit tests for eval_train_metric

* Update R-package/tests/testthat/test_basic.R
Co-authored-by: James Lamb <jaylamb20@gmail.com>
Co-authored-by: James Lamb <jaylamb20@gmail.com>