Fix ELO calculation / Write "regenerate scores" task

[MarcLapierre]

The ELO calculations seem off.

Replace ELO gem with manual calculation.
Write task to recalculate all scores. (Match history table?)

[MarcLapierre]

view-source:http://www.3dkingdoms.com/chess/elo.htm

function CalculateRatingChange()

{

var Elo1 = document.rating.elo1.value * 1;

var Elo2 = document.rating.elo2.value * 1;

var K = document.rating.K.value * 1;

var EloDifference = Elo2 - Elo1;

var percentage = 1 / ( 1 + Math.pow( 10, EloDifference / 400 ) );

var win = Math.round( K * ( 1 - percentage ) );

var draw = Math.round( K * ( .5 - percentage ) );

if (win > 0 ) win = "+" + win;

if (draw > 0 ) draw = "+" + draw;

document.ratingchange.win.value = win;

document.ratingchange.draw.value = draw;

document.ratingchange.loss.value = Math.round( K * ( 0 - percentage ) );

document.ratingchange.percent.value =  Math.round( percentage * 100 ) + "%";

}