SRA runs should save data elsewhere and then symlink #408
Description
Currently, when running an SRA metadata sample table, the fastq files are saved directly in the data directory. However, this means that you can't delete the data directory to trigger a re-run of a workflow like you can in a non-SRA run, where it's just the symlinks living in the data directory -- because the downloaded SRA fastqs would be deleted as well.
Instead, fastq-dump should put the files in a separate directory (will need to think carefully about where this should be), and then symlink to data.