Fixes to Sim.js and content mod acceptance #560

[DanielNoord]

Building on discussion in #560 and #591 I have rewritten Sim.js to be a little less 'static'.

New lines in CM.Main.Loop() check for new mods and if any are found it reloads all relevant function needed for the calculations in Sim.js.

I believe this closes #560 and therefore also #591

[hyoretsu]

For the most part, yes, but it still broke on CM.Sim.CalculateGains since adding kitten upgrades needs to inject a new line

if (Game.Has('Misfortune #603')) {
 catMult *= 1 + milkProgress * 0.05 * milkMult;
}

[hyoretsu]

If this also conflicts somewhere, upgrades that lower building/upgrade costs also need to inject into Game.modifyBuildingPrice and Game.Upgrade.prototype.getPrice.

[DanielNoord]

CM.Sim.CalculateGains will be fixed in #593
If I get to that issue I will also check for Game.modifyBuildingPrice and Game.Upgrade.prototype.getPrice.