Query expansion and ES RawQuery syntax

• Added query expansion features to enable boosts, filters (comparable to Solr's fq and bq params) and alternative matchings (embedding a query with other queries as should clauses) irrespective of rewriting
• Allowed rule definitions for Elasticsearch using QueryStringQuery syntax

Basic clients for Solr and Elasticsearch

• Basic implementation of using Querqy without a plugin
• Clients for Solr and Elasticsearch
• Almost all Querqy features are supported