New analyzer: Cross Correlation (Pearson correlation coefficient)

Cross-correlation matrices of BOLD time-series are called functional connectivity (FC) matrices. The analyzer we currently have in TVB computes non-normalized cross-correlation at different time lags. So, for selfish and practical purposes I'd like to implement a more simplistic analyzer that computes the Pearson correlation coefficient (sadly widely used in the community).

Probably recycle one visualizer to display the resulting matrix.