Included computation of full_seed_range metrics

By this we mean metrics that can only be computed when all seeds are
evaluated so that, in particular, no std can be computed. The only
metric of this kind at this point is the average of the absolute values
of x-dependant biases ('avg-bias'). These metrics will only be computed
for datasets with a dataloader of the type
EIVData.repeated_sampling.repeated_sampling.