Use iterators and generators with Dynamic parameters

Converted from SourceForge issue 1864370, submitted by ceball
Submit Date: 2008-01-05 07:58 GMT

Currently, we can't use python's iterators or generators with Dynamic parameters.

This is because:

(1) we deepcopy parameter values; python currently doesn't handle deepcopy of iterators and generators

(2) we want to be able to pickle simulations; python can't currently pickle iterators and generators (same as reason as 2)

(3) generators and iterators can't have attributes; we need to store _Dynamic_last and _Dynamic_time on the value generators