DOC more accurate comment in class weight computation
FIX make sure laplacian in spectral clustering test is really PSD
DOC: more consistency in metrics docstrings
DOC: More consistency in metrics and clustering metrics docstrings
DOC: more consistency in docstrings for unsup clustering metrics & missing link
DOC: fixed missed details in metrics docstrings
DOC: addressed more inconsistencies in metrics docstrings
ENH when possible use PCA instead of SMACOF for MDS