Suggestion - Prioritize "Efficiency" upgrade when Metal challenge detected

[entropiccode]

While Metal is typically an early game challenge, I noticed when running AutoTrimps during the challenge it automatically factored in the lack of Miners, however it made no considerations for the Efficiency upgrade.

Given that manual mining is the only source of metal in this challenge until maps are unlocked, AutoTrimps should prioritize purchase of the Efficiency upgrade above everything else prior to Zone 6, as each level of Efficiency doubles metal income. Waiting and saving metal to purchase Efficiency first is much faster than spending metal on the cheapest available building/upgrade/equipment as normal and waiting for Efficiency to become the cheapest option.

Efficiency is less important following Zone 5 in the Metal challenge as metal from map farming becomes the primary source at that point, however it would be a nice adjustment to streamline zones pre-zone 6, as it can be a difference of more than 30 minutes per zone.