Safe, informative calico.repr() function for all types

[Doug Blank]

Should not crash on too big, or recursive structures, and show nice, pretty-printed results for many types (IEnumerated, lists, dictionaries, etc). Replaces #167. Should be called in Calico GUI and in ICalico.

[Doug Blank]

Also needs to only be used on Output... calico.display() should use ToString() not Repr().

[Keith O'Hara]

Why ToString and not Repr?

[Doug Blank]

Repr will put quotes around a string; ToString doesn't. Side-effect string output looks weird if it has quotes around it.

[Doug Blank]

Added IList and IDictionary to notebook... need to add to GUI. Don't know how we managed for so long without these! It does show them using Python syntax.

[Doug Blank]

Added recursive safety (eg, won't go into an infinite loop on recursive data structures).

[Doug Blank]

This is still an issue in Calico Scheme running under Python.