Support installing Adept into the file system

Adept currently doesn't follow the Linux/Unix FHS, and there is no support for installing it into the file system either, as it's designed to be standalone.

[IsaacShelton]

Yes it would be nice to have an option to be able to easily install it in the conventional FHS way for Linux/Unix systems.

It would probably go well with having it in the various package repositories too, although I am unexperienced with creating these kinds of scripts in a portable way, so it might be better for someone who knows how to do this properly to create, test, and maintain this functionality.

It would be a good thing to add, although I don't believe I currently have the time to correctly create, test, and maintain these.

Feel free to make a PR though