CLI API?

Would be nice, to have a CLI API where you can enable/disable packages. For `buildout.coredev` and operations in general that would be so much nicer:

To enable a package, that is already configured:

```shell
mxdev enable plone.batching
mxdev -c mx.ini
```

And to disable:

```shell
mxdev disable plone.batching
mxdev -c mx.ini
```