Include raw_forward_seqs, raw_reverse_seqs, raw_barcodes in the preparation information

[wasade]

trafficstars

Local users often need to obtain the raw file paths for a given sample on a given prep. At the moment, this information needs to be inferred. Providing the columns within the prep would be very helpful. An example of how this could be done is in /home/qiita/pull-prep-connections-full.py