fix(drops): Overhaul drops to a percentage multiplier system

WIP. Initial draft of an overhaul to drop chance. Most important bits: (1) A modular system of percentage-based multipliers on the task-value-based initial drop chance. (2) Perception increases the daily drop cap by 1 per 10 points.

Fixes HabitRPG/habitrpg/#1922.
fix(drops): Increase base value, improve comments
Merge branch 'develop' of https://github.com/HabitRPG/habitrpg-shared into sabe/drops
fix(drops): Further overhaul drop chance

Reduces the divisors for several modifiers to give them a more noticeable effect (especially PERception, so Rogues continue to be durn sharp).
Merge pull request #155 from HabitRPG/sabe/drops

Overhaul drop chance to a percentage multiplier system