Add random_score  support for function score query
Merge pull request #412 from vovikdrg/random_score

Add random_score  support for function score query
spaces to tabs on TermsStats
fix #413 should not render an empty facet_filter block on facets with conditionless filters
fix #414 implemented a Conditionless() construct on filters and queries so that you can control what to fallback on
abstract facet did not extend IFacet