Steps to reproduce

1. Add an object with a bot attribute to e.g. chat_data and persist it

2. Change the bots token and restart the updater

Expected behaviour

The reloaded bot should have the new token.

Actual behaviour

The bot in the loaded chat_data still has the old token. Similar for the other bot attributes

Proposed solution

1. Remove __reduce__ from Bot , as we don't want to encourage pickling bots

2. Add static methods replace_bots(object) and set_bots(objects, bot) (or other naming) to BasePersistence, where replace_bots implements the logic to replace every Bot instance in an object, be it a dict, a list, a custom object … with some special placeholder BOT_INSTANCE or whatever and set_bots in turn replaces BOT_INSTANCE with the given bot. To make get_*_data and update_*_data use those, we have several options:

   1. Just call them in get/update_. Custom subclasses of BasePersistence will have to adjust.
   2. Add a __new__ method to make the get/update_ methods call the methods under the hood. that way custom subclasses don't need to change anything
   3. Add methods get/update_*_replace_bot, which call set/replace_bots and before/after get/update_*. Use those in Updater. This way, custom classes also don't need to be changed.

   don't know, whats better …

3. Alternatively to passing the bot to set_bots, we could add set_bot to BasePersistence so that we can use self.bot in set_bot. That would save us from having to pass bot to get_* as well