Windows 32bits / 64bits mixup

[paulrouget]

There are 2 strange things going on with the registry key path.

• sometime Windows doesn't do the wow6432node bypass when installing
• some special version of firefox (portable and waterfox) do not rely use wow6432node even though they run in 64 bits mode

To address both problems, we should force the registration of the coapp path in both Wow6432Node and not-Wow6432Node.

I'm not sure yet how to do that, but that seems the right approach.

This would also solve the problem of mixing up different bits-version of Firefox/CoApp/Firefox.

See #195 and #201.