Groovy is deprecated in ES 5.0, and it seems it already has been removed in the development branch for ES 6.0.

We must wait for HSearch 6.0 to do the switch though, because it has an impact on how users should configure their ES server.

We'll have to update the documentation once we did the switch.

Setting priority to critical since it will probably prevent us to support ES6 before HSearch7 if we forget to do it...