added multilabel datasets: scene and yeast

This PR is part of issue [# 1987](https://github.com/shogun-toolbox/shogun/issues/1987)

I have added scene and yeast datasets from http://www.csie.ntu.edu.tw/~cjlin/libsvmtools/datasets/multilabel.html

The datasets are also related to entrance task [# 1916](https://github.com/shogun-toolbox/shogun/issues/1916) and I may use them in [# 2018](https://github.com/shogun-toolbox/shogun/pull/2018).