Added facet handling. Still pending:
* facet ordering
* facet blacklisting
* multi-select tagging for filter queries
Merge branch 'develop' of github.com:rmerizalde/opencommercesearch into develop
add trait to easily add facets to the solr query in the api controllers
Merge branch 'develop' of github.com:gsegura/opencommercesearch into develop

Conflicts:
	opencommercesearch-api/app/org/opencommercesearch/api/service/MongoStorage.scala