update collect_bids to use deep copy for subject/session inital dictionary
update collect_bids to use deep copy for subject/session inital dictionary

oesteban/preprocessing-workflow,poldracklab/fmriprep,chrisfilo/fmriprep,poldracklab/fmriprep,oesteban/fmriprep,poldracklab/fmriprep,shoshber/fmriprep,oesteban/fmriprep,oesteban/fmriprep,oesteban/preprocessing-workflow,poldracklab/preprocessing-workflow,shoshber/fmriprep,poldracklab/preprocessing-workflow