Index operations

[jvanz]

We need to define and document a process to create and maintain the Elasticsearch index. In a recent bug, I've manually re indexed the documents in the Elasticsearch index used by the project to make possible highlight text in big text fields (source_text). It was a manual procedure and it is not documented anywhere. This made me think that we need to define an standard procedure for this kind of task. Otherwise, we will not share this knowledge with the community relying in a small number of people which might not be available (for any reason) when necessary.