Add DMSO and Sildenafil to list of test CCD cif files

• In previous work I found that SOx groups could cause problems.
• Please look up DMSO and Sildenafil (Viagra) in PDBeChem and add to directory with test cif files.
• How do the molecules perform in current tests?
• When committing the files you must include where the files were obtained (exact url) in the commit message.
• Include reference to this issue number in the commit message. See https://docs.gitlab.com/ee/user/project/issues/automatic_issue_closing.html