ROC Framework

Turns out less of my code was applicable to this than I thought but I am still interested in seeing this through! I was also a bit sad when I realised there are no python wrappers in libfacerec standalone because I was planning to do the whole thing in python lol.

Here is my idea for a rough framework of the ROC example. Anyways pretty standard have some loop through a bunch of thresholds and record the results for plotting later on. I think this will become more clear after we refactor to return the distances. Also I'm not totally sure how we want to handle the ROC curve because this is multiclass classification (all my code was for binary classification true positive, false negative etc.). I think the end goal is just to show how changing the threshold affects performance right? So people realise that they should take some time to adjust the thresh. In that case we can probably just plot something that demonstrates this.

Also, I did test this the orl database so the code works, its just not doing everything we want.