[ENH] Interface for MRTrix's tcksift

[GalKepler]

Summary

It should be beneficial to have an interface for MRTrix's tcksift as part of the overall effort to include as many as possible of the tools being used in the neuroimaging society.

Expected behavior

Being able to use a dedicated interface for tcksift, that would, at it's most simplified case, look like this:

from nipype.interfaces import mrtrix3 as mrt
tcksift = mrt.TckSift()
tcksift.inputs.in_file = "/path/to/streamlines.tck"
tcksift.inputs.in_fod = "/path/to/fod.mif"
tcksift.inputs.out_file = "/path/to/sifted_streamlines.tck"

tcksift.cmdline

tcksift /path/to/streamlines.tck /path/to/fod.mif /path/to/sifted_streamlines.tck