core/app: fix abbreviated option parsing with identically named options (-std --> [-stdev, -stdev] in mrfilter)
core/app: fix abbreviated option parsing with identically named options (-std --> [-stdev, -stdev] in mrfilter)

MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3