Request tweaks

This covers a number of changes to how requests are handled:

• The biggest change is that requests now need to live for a minimum amount of days before they can be randomly discarded. This allows requests to accumulate again, to some degree. More specific discard rules such as all spring cleaning requests being dropped after winter are not affected by this and will continue to apply as usual.
• Significantly reworked the request generation mechanic, replacing the old @IRAI_HAPPEN.
  • Baseline generation attempts increased from 10 to 15.
  • Characters living on MAIN_MAP get rolled for a second time, giving them around three times greater odds of generating a request.
  • Duplicate numbers and invalid numbers no longer happen
• As players complete requests, they gain a Helpfulness score.
  • Higher Helpfulness increases the rate at which requests are generated, and it increases faster the quicker requests are accepted and completed.
  • Ignored or failed requests lower the Helpfulness score, with the reduction increasing the higher Helpfulness was, which should make the system fairly self-balancing.

In my tests, a 0 Helpfulness character can accumulate around 30-35 requests before they start disappearing, which gradually ramps up to around 50-60 if the player does a lot of requests. Ignoring them will cause the score to drop back down very quickly again. This should provide players with an opportunity to focus on doing requests, if they want to.