cleaning
debug: sin(Theta) needs a complete decomposition

sin(Theta) is computed as QExactKBot.T.dot(QApproxK). Beforehand,
NingsSpectralClustering and IterativeSpectralClustering were using a partial
"exact" decomposition to have QExactKBot, which was wrong. Nowon, the
decomposition is complete (obtained through scipy.linalg.eig and
scipy.linalg.eigh).
exp/sandbox/Nystrom.py

enhencing code reading
enhencing code reading
debug: sin(Theta) in NingSectralClustering

In Ning's approach, relevant dimensions are the one with smallest eigen values,
while the current implementation was evaluating sin(Theta) on dimensions of
greatest eigen-values.
add Ning to growingContrast graph
reordering curves
debug: constant sin(Theta) values