Zeiss CZI: prepend 0s so that image names are all the same length

See QA 10335 and
https://www.openmicroscopy.org/community/viewtopic.php?f=13&t=7681
Merge pull request #1412 from melissalinkert/czi-name-padding

Zeiss CZI: prepend 0s so that image names are all the same length