Sprout from master 2017-02-10 17:53:35 UTC Moises Fernandez <moisesf@fmrib.ox.ac.uk> 'Corrrect division by zero bug'
Cherrypick from master 2015-02-03 17:45:22 UTC Moises Fernandez <moisesf@fmrib.ox.ac.uk> 'Count crossed positions of Matrix3 only if the current part of the path is accepted':
    probtrackx.cc
    streamlines.h
Delete:
    testfile.cc

Do not write path distribution without --opd argument (it was being written with only --ompl argument)

Correct bug: triangles crossed by a seed that is a voxel are 0, triangles value is -1 to identify that is part of a volume (not part of a surface)

Correct bug: triangles crossed by a seed that is a voxel are 0, but must be indicated with a value -1 to identify that is part of a volume (not part of a surface)

Correct bug: triangles crossed by a seed that is a voxel are 0, but must be indicated with a value -1 to identify that is part of a volume (not part of a surface)

New option to count only the nearest neighbour vertex when the face of a surface is crossed and avoid connections between vertices of the same triangle

Allow propagation after crossing the surfaces of wtstop mask: now it does not stop after the first jump just after crossing a surface, it continues until it crosses that surface (or another) for the second time