Add method to know if you are in a script

[kmvanbrunt]

I frequently use command finalization hooks to print something just before returning to the prompt. I don't want the output to occur after each command running in a Python or text script though.

Currently I do the following to know if I'm in a script:

if self._in_py or self._current_script_dir is not None:
    # In script

It would be better to provide developers with a method so they don't have to reference protected members.