[ENH] Interface for tcksift2

[GalKepler]

Summary

It should be beneficial to have an interface for MRTrix's tcksift2 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 tcksift2, that would, at it's most simplified case, look like this:

from nipype.interfaces import mrtrix3 as mrt
tcksift2 = mrt.TckSift2()
tcksift2.inputs.in_file = "/path/to/streamlines.tck"
tcksift2.inputs.in_fod = "/path/to/fod.mif"
tcksift2.inputs.out_weights = "/path/to/streamlines_weights.txt"

tcksift2.cmdline

tcksift2 /path/to/streamlines.tck /path/to/fod.mif /path/to/streamlines_weights.txt