Support multi-echo SBRefs.
Support multi-echo SBRefs.

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