Don't store any profit data in the save, compute it when needed from income and expenses

From conversation in #2104 (closed). This reduces the size of $lastWeeksGatheredTotals by about 1/4, and eliminates $lastWeeksCashProfits and $lastWeeksRepProfits, which are both large structures in their own rights.

All the reports look correct in testing, the game is just a bunch smaller.