Tract profiles of approximated qMRI

[arokem]

Following Moskovitch et al..

I guess that right now our approach would be: "Calculate these things separately and point pyAFQ to the derivatives", so arguably out of scope for pyAFQ itself.

Maybe it needs to be a separate project? Or is it part of qsirecon?

Tagging @mattcieslak who also wants to make this happen.

[mattcieslak]

This is very high on my list of features to add to qsirecon. We currently calculate a TON of other scalar maps that we'd like to make tract profiles on