hypermat - initialize an N dimensional matrices
Initialize an hypermatrix whose dimensions are given in the vector dims and entries are given in optional argument v
M data structure contains the vector of matrix dimensions M('dims') and the vector of entries M('entries') such as the leftmost subcripts vary first [M(1,1,..);..;M(n1,1,..);...;M(1,n2,..);..;M(n1,n2,..);...]
M=hypermat([2 3 2 2],1:24)