Allow automated user pit archival in general

[cyrus01337]

^{_{This is a tracking issue, by the way.}}

There already exists methods to automatically archive user pits when a member joins and leaves. At the moment, the only way to determine when a user pit is inactive is through mod discretion - human effort. While this may not be considered negative, it is something that mods must factor into their role, which a solution to this will aim to solve.

By default, all user pits will be automatically archived if left unused for a week. This duration should be configurable (options up for discussion), including the following sensible (I think anyway) choices:

• 24h
• 3 days
• 1 week
• 1 month