[FEATURE] aggregrated global evaluations

[neuronflow]

Is your feature request related to a problem? Please describe.
sometimes, multiple patches are evaluated that come from a bigger entity, e.g., multiple microscopy slices from one brain. computing aggregated statistics on a patch level leads to different treatment of blobs depending on their patch. E.g. one patch might gave 5 instances another 100, so the instances from the less populated image volumes have much bigger impact on the aggregated statistics.

Describe the solution you'd like
a flag to aggregate globally, "across" image volumes.

Describe alternatives you've considered
for RQ it is quite trivial to compute this from the confusion matrix, but for SQ it is not so easy.