Adds a new component Upkeep similar to ResourceTrickle but to allow for entities costing resources instead of providing them.
A separate component because:
- ResourceTrickle is not suited for negative rates and the adaptation thereof would make it unnecessary complex.
- "We" may want to introduce effects to happen when upkeep cannot be paid.
Ideas for penalties of not being able to provide the necessary resources include:
- Decline of HP.
- Conversion of CP to GAIA.
- Reduced effectiveness of the entity (e.g. workrate, attackpower, productionrate).
- Uncontrollability. <- Chosen in this diff.