Automatically download win32 builds for Mapeo Desktop

[okdistribute]

We separated the Windows 32 build for Mapeo Desktop into it's own executable which is great because it makes the footprint much smaller, but now if you're on a Win 32 machine and go to /mapeo/download, you'll get the 64-bit version.

We need to change the script in mapeo/download.html to check if the user is on 32 bit Windows and download that instead of the 64 bit one