Make elastic search proxy bundle agnostic to the project

Use events for modifying request
Oh, you're talking about the request to ES. I was talking about the request that has just come in. Sounds like there is already enough ambiguity to cause confusion. Since we're dealing with 2 sets of requests and responses, it's another reason to be more verbose with event names. 

There are 2 "requests" in play here:
1. Symfony request that just came in
2. Elasticsearch request that you are going to make

Probably best to call it `elasticsearch_proxy.before_elasticsearch_request`