Allow custom data directory

[evandrocoan]

I installed it on Windows, and the prompts are saved on C:\Users\Username\.nofwl. I would rather save them on D:\nofwl, so if I format my computer unexpectedly, my data would be saved in a save location.

It would be fine to save the data alongside the application itself. I installed it on D:\nofwl. For example, the Sublime Text editor automatically saves its data on the current executable directory if it finds a data directory alongside the main binary. If you could follow the same strategy would be more than enough.