repreprocessing from dicom tarballs with --overwrite would fail since full paths to tempdirs were recorded

[yarikoptic]

I think that is one of the aspects I might have broke/changed from how heudiconv performed originally -- I believed no full paths were stored within .heudiconv/*/info so processing could be redone even if dicoms were in a tarball (extracted to a temp dir)

Ideas:

• echoing saving of hidden files that are not updated with changes to heuristic #84 may be we should add an option (e.g. --disregard-info or alike) to allow to disregard previously collected info and just redo conversion
• consider storing relative paths to dicoms somehow?