ENH: Add tutorial comparing vanilla DTI with warping a high-quality scan back to lower resolution dMRI data

[alexrockhill]

With low resolution/direction dMRI data, you have limited options for tractography and will suffer from losing crossing fibers when using DTI. We could show this in a tutorial. You could also use a template with good labels and try and SDR morph it back, probably on the FA maps, that's a good question though. @pjsjongsung said he'd look around and see if this was done so making an issue for that info to persist.

[alexrockhill]

A suggestion from Dianne Patterson was to use HCP data which seems like a no brainer.