First developments for querydsl-elasticsearch.

Hi,

I used `querydsl-jpa` and `querydsl-mongodb` with the Spring integration. I recently install an Elasticsearch cluster for analytics purpose with `sping-data-elasticsearch` bridge. Nevertheless the named query methods in spring is not type and name safe, which I really like in querydsl features.

So I have developed a first integration of elasticsearch in querydsl. Currently the implementation allows to run "classic" operations such as `EQ`, `BETWEEN`, `AND`, `OR`... There's a query factory *JacksonElasticsearchQueries* to create the queries by Q-type, elasticsearch index and elasticsearch type. We could also customize serializer and/or transformer.

I didn't write documentation about it, do you have some advices to give me ?
I hope this PR will help the project.

Bye
Kevin