- dummy index recognition in products was flawed: A.i.i*B.j.j would be

- dummy index recognition in products was flawed: A.i.i*B.j.j would be
  treated as a scalar product of A and B, A.j.j.i.i*B.k.l would be 0
  if A was symmetric and B antisymmetric etc.
- removed redundant code for handling d.akl*f.akl contraction; this is
  handled by simplify_indexed() itself since it is a contraction of a
  symmetric with an antisymmetric tensor