Each row of the matrix corresponds to a row of INFINITESIMAL_MOTIONS and
contains its expansive pattern, i.e. each entry describes the behaviour of
an edge of the complete graph under the corresponding motion:
If the entry is positive the edge expands,
if it is negative it shrinks,
if it is zero the length stays fixed.
The order of the entries in each row correspond to the lexicographic
order of the edges of the complete graph on N_NODES nodes, i.e. (0 1), (0 2), ... , (0 N_NODES-1),
(1 2),...,(1 N_NODES-1), (N_NODES-2 N_NODES-1).