Add fold change or PLAGE score to PALS Viewer

[joewandy]

Justin suggested, when analysing motifs or molecular families, we can compute the fold changes or the PLAGE score. This could be displayed to users.

Not sure if it makes sense in the context of pathways.

[RonanDaly]

Tried to do this before (you might remember code that I had left in near the svd, but wasn't able (at the time) to come up with something that made sense (as an average e.g.)