New Graphics: network & cim

New S3 method network and cim for results from PLS model
New code for the valid function to PLS-DA and SPLS-DA models validation
The S3 method plot.valid was modified to display graphical results from valid function for PLS-DA and SPLS-DA models
cim and network functions were modified to obtain the similarity matrix in return value
The S3 method plotVar was modified to obtain the coordinates for X and Y variables in return value
The predict function has been modified to simultaneously run either several or all prediction methods available to predict the classes of the test data from PLS-DA and SPLS-DA models