Nix packages support, how to expose to users.

We'll have to think about how to expose nixmanager to users, as discussed at devsync. some deliberation already happened in the telegram group but we did not acknowledge the fact of competing standards, and if we put everything in the settings app it will be confusing for sure.

courses of action I see (feel free to suggest more):

1. keep in system settings (as is).
2. make it an openstore app
3. aggregate it Libertine/NixManager under a list submenu for packages in system settings. (or make it an official category of plugin i,e system,personal,ect... packagemanager)