update standard web.config to support upload of larger files.

I'm setting up a webshop of downloadable Products that are larger than the standard 4Mb in size. I had to make Changes to the web.config to handle this. (size and timeout).

My suggestion is that the web.config in the downloadable zip archive is updated to handle this out of the box so that everytime I install a new webshop I don't have to google and make these Changes again.

Thanks a lot for suggestion. Here is a work item