Implemented the Blitz++ trick to allow the initialization of lists and matrices

Implemented the Blitz++ trick to allow the initialization of lists and matrices
from comma-separated sequences of expressions, like this:

  lst l;
  l = x, 2, y, x+y;

  matrix M(3, 3);
  M = x, y, 0,
     -y, x, 0,
      0, 0, 1;

This is both faster and produces much smaller code than the old constructors
lst(ex, ex, ...) and matrix(unsigned, unsigned, lst), especially in the case
of matrices, and is now the recommended way to create these objects.