Apply good pixel mask diff

This merge adds the capability to automatically mask pixels in the differential front end which have a too high parasitic capacitance at the discriminator output. The mask is based on the "proposed good pixel mask" as shown here: https://indico.cern.ch/event/724185/contributions/2978573/subcontributions/253619/attachments/1644974/2628708/DiffFE_radMtg_May7.pdf

The feature can be enabled by setting the 'mask_diff' : True, argument in each scan routine. By default it is disabled.