Devops tweaks in Vagrantfile and package.json (reberhardt7#43)

Make the following tweaks to the build system files (mostly `Vagrantfile`):

- Forward port 9229 from the VM. This allows attaching a debugger to the Node server.
- Add a corresponding `serve-debug` script, to run the server with debugging enabled.
- Disable the redundant `/vagrant` sharefolder; we already share the relevant contents via `/cplayground`.
- Run the provisioner which loads the cplayground kernel module every boot. This makes the development VM resilient against `vagrant halt` / `vagrant up`.

It looks like the Node debugger has potential for [live reloading](https://www.jetbrains.com/help/webstorm/running-and-debugging-node-js.html#nodemon), which might be nice. (I have not investigated.)

Disclaimer: I'm currently having issues attaching to the Node instance with this tweak. I think it's a me problem as I'm pretty sure I've used a config very like this successfully before, but it's probably worth testing.