[FEATURE REQUEST] Option to not delete paired files

[kenanoestreich]

It would be helpful if there was an option to run dcm2bids without deleting the source data that gets paired. There have been times where I didn't put everything I wanted in my dcm2bids_config.json but enough to get the right files. In this case, renaming all the nested directories and files isn't tenable and often making a backup of the whole directory before running dcm2bids is also tedious as the directories may be quite large.

Something like --keep-paired-files would be nice to just not touch the data in sourcedata/.