Revert "ignored mex files experiment_multiclass now is not standalone anymore, deleted clean, prepare, collect and experiment files"

This reverts commit 885fa5925d4c8bf9411b97adfc0b5e5210e00029.
Revert "Revert "ignored mex files experiment_multiclass now is not standalone anymore, deleted clean, prepare, collect and experiment files""

This reverts commit 55afbcdb77692628ea2ce63f360cc99c4e1715f1.