Remove vstack_features -> use the one in bob.pipelines

See merge request !187

Wrappers and aggregators

See merge request !185

Detached the mechanism of writing scores from the BioAlgCheckpointing. This will allow us to write different score writes for different analyser

Wrapped the vanilla_biometric in a class called VanillaBiometrics. In this way the user has to dask_it this only once and not twice as before, making the user code cleaner

Created optimization that allows you to do fast scoring if such option is available in the BioAlgorithm AND the database allows you to do it. I still think that the Vanilla Pipeline should be in a class. This will come in a next MR