Adding periodic bot self leave functionality after a certain timeframe

[SocksTheWolf]

The easiest implementation is to do the following:

• Start documenting in the DB when a server was added to the database (this may be able to be fetched via metadata, but likely requires a new column)
• Periodically check the DB to see what instances are after a certain amount of time (need to determine the window, 7 days should be good)
• Have the bot autoleave the server (can call LeaveServer from the main instance).

For ease of use, it might be better to just have the main ScamGuard instance run this periodic functionality (via the Task system) for us, as it's LeaveServer call will auto-resolve the correct server for us automatically.

The plus side for this is the following:

• Less instances running = More memory saved
• DB Queries are less expensive
• Starts cleaning up the database for us

The downside is:

• Users may get confused thinking they have ScamGuard but it's no longer there. This might be alleviated with extra messaging features from Post a message on join #57 but that feature is not necessary for this issue to be completed.