Add new Elasticsearch Mapping Generator

Description

Add a complete rewrite of the Elasticsearch mapping generator

Explanation

The old mapping generator is very messy spaghetti code that is going to be a nightmare to maintain.

Mockup

1. Use a JSON-Schema-Generator as a base. It already does 90% of the work we need, as ES mappings are structured very similar to JSON-Schema.
2. Reuse old tests