- Instead of just totally symmetric or antisymmetric, complex symmetries

- Instead of just totally symmetric or antisymmetric, complex symmetries
  can now be defined for indexed objects. Symmetries are described by a
  tree of "symmetry" objects that is constructed with the sy_none(),
  sy_symm(), sy_anti() and sy_cycl() functions. The symmetry of a function
  with respect to its arguments can also be defined (this is currently
  only used for the Beta function).
- color_trace() and dirac_trace() can be applied to a more general class
  of expressions, e.g. using it on a relation will take the trace on both
  sides etc.
- Generalized map() to take a function object instead of a function pointer.
  This allows passing an arbitrary number of additional state to the
  function being called.
- The unarchiving functinos find_bool(), find_unsigned() and find_string()
  can take an additional "index" argument.