Foreshadow object serialization and deserialization plus a simple python script wrapper

[jzhang-gp]

Description

• Foreshadow object (de)serialization including the data preparers and the estimator. Note that for the estimator, if a user uses a pipeline rather than a single estimator, we cannot guarantee there is no verbose output in the serialized file.
• Included a simple oneliner script to run foreshadow from command line: ./bin/foreshadow_runner.py <data> <target>

[jzhang-gp]

The new changes has removed the CustomizedParamsMixin completely since we can just use deep=False in get_params and dict_serialize. In fact, we should probably default deep=False. I don't see a use case where we are using deep=True? The whole CustomizeParamsMixin and many other customization around (de)serialization were based on the impression that we use deep=True, which generates a lot of verbose data we don't need to show. For now I hardcoded a few places to use deep=False when overriding parent's dict_serialize. If this makes sense, I'll change the function signature to use False as the default value.