fix(strength): Remove threat reduction, increase crit chance

Tweaks the STR attribute's algorithmic effects. (1) Task "redness" no longer declines faster with high STR. (2) The 3% chance of a critical hit is multiplied by a percentage factor equal to STR. (3) The value of STR in dealing damage to bosses is increased by 25% (.5% instead of .4%).

Fixes HabitRPG/habitrpg/#2464.
fix(drops): Ratchet up base chance some more

Ups the base drop chance to an expected 15% for typical tasks, brings back diminishing returns for super bonuses, reduces effect of checklists. Should be acceptable to most people?
Merge pull request #166 from HabitRPG/sabe/strength

STR and drop chance revisions