changed usage of DataElementState->start_from_scratch to have step_numbers be a named option, allowing optional new anti_repeat_store option, which is used by DataSourceRole _start_over_elements_due_to_file_metadata_change and datasources to avoid starting from scratch the same things multiple times in a single loop
updated author-only test skip to new host used by author
reimplemented File::copy to preserve mode and ownership, which also applies to move() in check_md5s mode
Merge branch 'develop' of /software/vertres/git/origin/vr-pipe into develop