fmriprep --minimal mode

[effigies]

A version of fmriprep that produces a set of derivatives necessary to support fmriprep-apply and nothing else.

Minimally, this requires:

• STC parameters (should be part of input)
• HMC estimates (Output motion transforms in BIDS Derivatives #2803)
• SDC estimates (Output SDC transformations as voxel displacement maps #2804)
• Masks
• BOLD-T1w registrations
• T1w-template registrations

[Lestropie]

Relates to #2207.

[effigies]

@Lestropie I really hoped to be able to get to this during July, but failed. I'm now going to be out for three weeks for vacation and a dedicated sprint on another topic, so hope to be able to start to get back to this the week of Aug 22.

Please do feel free to push on PRs or add notes of any roadblocks you're having or things you need input on.