Allow definition of descriptive and target attributes

At the moment, the wrapper is defined to automatically assume the indexes for the descriptive and target attributes. Since sometimes we need to define this by hand (e.g. exclude some attributes of the dataset in the descriptive space), my suggestion is to comment out/remove the lines that are used to set this: lines 607 - 610 in clus.py. I tried it locally, it works ok with this fix.

If you need more info from me, reach out.

Thanks!

Sintija