Fix advanced help alignment

OME-DCO-1.1-Signed-off-by: Sebastien Besson <seb.besson@gmail.com> (github: sbesson)
Yet another alignment commit

OME-DCO-1.1-Signed-off-by: Sebastien Besson <seb.besson@gmail.com> (github: sbesson)
Add leading -- to --checksum_algorithm using bin/omero import
Merge pull request #2828 from sbesson/rebased/dev_5_0/rebased/develop/cli_import_help_another

CLI import help changes (rebased onto develop) (rebased onto dev_5_0)