Previous APPX packages were 32-bit by default. At some point this
switched to 64-bit by default, but I didn't notice because the APPX
release was blocked at the time. This change enables both, which seems
ideal the MS Store will choose the right build for a given client.
Use 'nsis:ia32' instead of just 'nsis' for the Windows direct-download
build. This means we explicitly request a 32-bit build rather than
allowing electron-builder to default; the default is currently to make a
64-bit build.
resolves#114
