Provide packages for Linux, macOS, Windows using fbs

[mardukbp]

Yesterday I came across the fman build system, which considerably simplifies the process of deploying a PyQt app in all three operating systems. This would be a big boost for Qnotero.

[smathot]

Thanks for your suggestions. However, I'm not actively maintaining Qnotero for the moment. I'll archive the repository to make that clear.