[PATCH] Clean up Looter.js

[Stan]

cmpStatisticsTracker.IncreaseLootCollectedCounter(resourcesToAdd); is called identically twice, and there are some other things that can be cleaned.

[Stan]

Initial Elexis's patch

[elexis]

fcxSanya implemented Looter.js in r9391 and r11279.

We should clean this code before adding more code, like #2732.

• added comments
• removed reundancy by summing up the looted resources and then transfering them and updating the statistics only once)
• not 100% sure about the call to ApplyValueModificationsToEntity. In my testing it gave the same results, so we might not need to update resources with the return value. In doubt, revert that line.
• conditional operator to improve readability
• let instead of var

[elexis]

Visually replaying this file proves that my patch doesn't work as sometimes ApplyValueModificationsToEntity can return something different from what values it received. (Non-visual replay only checks every 20th turn, while visual-replay checks every turn).

[elexis]

Reverts that ApplyValueModificationsToEntity line and further simplifies those resources[carriedGoods.type] += carriedGoods.amount.traderGain || 0 lines.