Hibernating Cities

[JonathanSafer]

Rather than unclaiming cities, cities should have one or more hibernation modes where they stop producing creeps entirely, except for the occasional upgrader (possibly a unique role) to maintain the claim. Hibernating cities will be able to semi or fully come out of hibernation to defend themselves, maintain walls, and/or generate economic output when there is significant spare cpu (peacetime). Cities designated with hibernating ability will be able to hibernate to create excess cpu during times of need.

[JonathanSafer]

Considering how low cities can stoop when on low CPU, this may no longer be worthwhile unless we are going for a record number of rooms on shard3