(s)PLS-DA added

plsda and splsda functions are implemented to perform PLS Discriminant Analysis (PLS-DA) and sparse PLS-DA respectively
breast.tumors data set is introduced to illustrate the (s)PLS-DA
PCA can also been performed with missing values using the NIPALS algorithm and 3D plots are also available for PCA
Network (updated) to display relevant associations between variables for (r)CCA and (s)PLS, with a new similarity function
A new similarity measure has been included in cim function and the arguments hclusfuncand distfunc to display Clustered image maps (heatmaps)