Add missing figures to report

[tsalo]

Closes #947.

• T1 to MNI registration (<source_entities>_t1w2mni.svg)
• diffusion summary (<source_entities>_desc-summary_dwi.html)
• DWI sampling scheme (<source_entities>_desc-samplingscheme_dwi.gif)
• SDC
• bias correction (<source_entities>_desc-biascorr_dwi.svg, <source_entities>_desc-biascorrpost_dwi.svg): DSDTI_synfmap
• b0 reference image
• dMRI and anatomical coregistration
• DWI summary

Changes proposed in this pull request

Documentation that should be reviewed

[tsalo]

I'm seeing all of the figures in one HTML or another, so I think the problem must be that the entity selection step is somehow excluding some files because they have different entities from the "source" file (whatever that is), probably because of how entities are changed when QSIPrep concatenates data across runs, acquisitions, etc.