mdlhist doesn't form histories of states placed in dictionaries

[hulsed]

State return should copy states instead of reference them, when possible

[hulsed]

Need to define this problem better--as of present, state return seems to work fine for sets, lists, and plain values.

• What is needed for a dict history and what is the use-case? If dicts are nested enough, copies will need to need to be made of each value.