Refactor hash_obj to handle nested arbitrary objects

[ShiveshM]

Similar to how it's done in the normQuant function

backstory: When a Pipeline object is used as a Param value in a ParamSet, the ParamSet method values_hash fails to obtain a hash value. Inside the values_hash function, hash_obj is applied to a tuple of the ParamSet values, one of which is the Pipeline object. Currently hash_obj treats tuples (and all other Sequences) by converting it to a string using pickle. The Pipeline object is not picklable so it fails.

[LeanderFischer]

Still seems to be the case, but I'm not sure how serious this problem is :thinking: If someone feels up for it, they could try to implement it, apparently similar to the normQuant implementation..