Add option for ignoring anatomicals in recon-spec

[smeisler]

Summary

Specific case, but UKB anatomicals and DWI do not line up well due to obliqueness, and this causes problems. Right now the only usable recon-spec is dsi_studio_autotrack but it only works if the brain mask is derived from the DWI instead of used from the anatomicals. So, it would be nice to have an ignore anat option when using ingressed data that can be defined at the recon-spec level (such as not to over crowd the qsirecon argument space).

Additional details

Better enable UKB ingressed reconstruction.

Next steps

[tsalo]

What about an --ignore flag at the command line?