WS-1577 Quicklook imaging in pimscache
This modifies the pims_split workflow to iterate over the new splits list structure (i.e. splits -> {split_dir, quicklook_url}) in the metadata.json, dag, and split.sh files. This also sends a post request to the quicklook URL for the corresponding jobspec ID if the user ran pimscache with the quicklook option.