Converts from a mesh-matrix to vector representation
Returns a matrix in which each row corresponds to a point on the grid defined by the mesh-matrices X and Y. The enumeration of points goes from the top-left corner of the mesh to the bottom-right, columnwise.
cXcYcZ = gtm_m2r(X, Y, Z)
cXcYcZ = gtm_m2r(X, Y)
cXcYcZ = gtm_m2r(X)
X, Y, Z - mesh-matrices for x-, y- and z- coordinates respectively; M-by-N.
cXcYcZ - matrix of rows of tuples; (M*N)-by-k, where k is 1, 2 or 3