Scaffold a basic provider based on VirtualBox provider

Basically a set of `noop`s to later fill in with `vagrant-lxc` related code.

Initially supported actions:
* [x] up
* [x] destroy
* [x] halt
* [x] reload
* [x] box add

Reference:
* https://github.com/mitchellh/vagrant/blob/master/lib/vagrant/plugin/v2/provider.rb
* https://github.com/mitchellh/vagrant/blob/master/plugins/providers/virtualbox/provider.rb
* https://github.com/mitchellh/vagrant/blob/master/plugins/providers/virtualbox/action.rb
* https://github.com/mitchellh/vagrant/tree/master/plugins/providers/virtualbox/action