non-linear fatigue energy relationship

[nicidob]

Yeah so this replaces the linear fatigue energy relationship with a nonlinear one. Specifically, a sigmoid. This allows players to play at nearly their peak level, until the inevitable decline.

• I removed the "don't play too many minutes" thing since the non-linearity should be pretty steep
• I think the current settings (steepness 50, mean 0.85) are okay, but not exhaustively tested. Shifting the mean can cause the whole league to play only 25 MPG or 45MPG, and 0.85 gave me reasonable results (peak near 37 in the regular season, 41 in the playoffs)
• fatigue function has a single return point so it's easier do the transform in one place
• playing time scales energy, not overall. This lets it apply naturally to the non-linear curve

In my testing, this allows you to adjust PT (perhaps the current multipliers aren't well tuned). In general, decreasing PT won't increase one's stats significantly. I tried with one player and they went from 34MPG at neutral PT to 11MPG with [-] PT and their PER was +- 0.2 and BPM was +/- 1. [+] PT drove them to 40 MPG and halved their PER.

EDIT: Not sure if the playing time is correctly balanced right now. For example, check 2018 Real Players and check. AD is at 40MPG in normal settings. But only like 36 in this one.