loading function/class from python

[chengchingwen]

Since there are no function/class bodys in pickle but only module and function name, we can't not reconstruct the function or object in Julia.

proposed solution:

read names and maintain a mapping table for map from name to similar Julia function and objects. The mapping table is customizable, user can register custom function for a given name.
if not find on the table, raise exception, or optional fallback to use pycall