Update to batch script

I was having some issues with the download via powershell, so I updated the .bat file to first try the powershell method, then try an ActiveXObject method (via the wget.js script file) that has worked for me in other batch scripts.  I added some more success/failure messages and split out some of the zipping and downloading. I've also added some more checks for the build script (so it doesn't try to download or unzip if it's already available, or if not it checks at each step e.g. before download, then before unzip)