Fix decomposition bug

IPCA should receive data always with images in the rows. rowvar parameter is in charge of deciding whether the fit should be done with the rows (images) or with the columns (pixels). For this case, as in NICA we are interested in computing PCA with the pixels being the samples, NICA will pass the normal data to IPCA with the rowvar parameter to False. This way, no transpose of the data has to be done and data can be loaded from disk.