_instance.ownerId and bot ownership

[ffflick-gh]

First, add support for bot managers (basically co-owners) and a command for transferring ownership. Ownership can only be transferred to bot managers (for an extra layer of...security?).

And this change also calls for change to the _instance.json file:
Update _instance.json to replace ownerId with botOwner and appOwner.
This is because there will be ambiguity between whether ownerId refers to the owner of the app or the owner of the bot (which may change if ownership can be transferred).

To-Do:

• Add bot managers
• Add transfer ownership command
• Replace ownerId in _instance.json with botOwner and appOwner