Remove cmd

I stumbled over an issue when trying to fix the localproxy.go in /pkg/localproxy. Obfsvpn changed and the way it needs to be started, but this was not reflected in localproxy.go yet. While fixing that I realized that I actually cannot really test it, because the CMD is more fundamentally broken or experimental to use. I see the benefit of having a commandline interface to test out bitmask-core, but at the current stage we're at, it's distracting us from our main tasks.

That's why I would like to propose to throw out the cmd package completely and to create a separate repository for it. We might be able to revert that decision in the future and merge the CMD back into this repository, but at the moment we don't use it at all and it requires extra work to fix and maintain it - which we IMO don't have right now. In case a brave hacker wants to build on the CMD, there would be the option to do that in the separate repo without getting into our way in the process of integrating bitmask-core into the clients.