[tests] Centralize histogram production; Fix tests to only verify existing references and error if not all references are checked

Make code and tests flexible to the use of a pre-processed Montgomery dataset to speed-up testing where possible (closes #74)

[tests.test_resource_monitor] Be more verbose when multiple processes are running when they should not

[scripts.evaluate] Be more thorough with information saved after evaluation; Refactor plot generation; Add option to not plot; Add option to control binning (issue #64); Solve binning issue with large datasets (closes #64); Add test units

Histograms comme be compared directly due to differences in how the
torch.resize transform is applied depending on the environment.
A statistical approach using pearson coefficients is used instead.
Testing of alexnet and densenet transforms have been temporarily
disabled as histograms or RGB images need to be handled differently.

Databases should now be available on the CI, we do not rely on a zipped
db anymore.

Samples are not square cropped during data loading anymore due to recent
changes. Cropping is model-dependent.