Fixing IE8 errors

This pull request fixes all IE8 errors. It fixes #1731 

Please have a look, if it's ok to put the forEach function to the Array.prototype in the middle of another function (changesettracker.js). Maybe you want to add it more globally.

Also please note, that this is only the simple version. Here you find the full version: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/forEach#Compatibility