Added "add_user" and "remove_user" commands

[deejaypro]

• Added "add_user" function
• Added "remove_user" function

Added a regex match to "add_user", because it is only allowed to add email addresses to the list.

I needed those functions for my project and thought i might aswell create a pull request.

[deejaypro]

I also added the ability to delete messages with a function.
And i also added a function to remove the Message the bot sent after a specific amount of time. This helps with the clutter a bot can produce with the output

[deejaypro]

One restriction is, that it depends on the reply and the messageId from that reply within "process_incoming_message". This means that cards won't apply to this since it is handled by another function within the users code. So Cards need to call "async_deletion_start" with its parameters to deleted after a specific amount of time.