Self-Chat Improvements

Each of these could be spun into a sub-issue, and requires some scoping to be done. The following improvements could benefit self-chat in particular.

• Allow 2 models to be passed in e.g. apprentice, wizard, currently can't.
• Currently does not support standard batchworld (will need the world not to do anything fancy, maybe it's possible? This would be easier if batchworld accepted a generic 'contextWorld' with initial contexts, but we don't have that currently (we have talked about this for a while).
• General fix (beyond self-chat) but useful here: allow worlds to have args (currently only teachers are checked) so we can add flags more easily..
• Make interactive world share more with self-chat world where possible via inheritance.