Get autocompletion schema from preset.

[SebastianStehle]

At the moment, there is a hardcoded schema for autocompletion.

This PR removes that in favor of a schema that is created from the default preset.

Advantages:

1. Always consistent with the implementation.
2. It exposes the supported children, so it only recommends mj-carousel-image inside a mj-carousel.
3. It exposes possible values for attributes, so you get additional autocompletion.

I had to change the sass implementation from node-sass to sass, because I was not able to get it running under windows. It has dependencies to very old python versions.