FunctionScore: boost_factor function not supported

[Xylakant]

The boost_factor function is not supported since the signature for addFunction() expects the function_parameters to be an array, but the boost_factor accepts a single float value.

see https://github.com/ruflin/Elastica/blob/master/lib/Elastica/Query/FunctionScore.php#L61 and http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/query-dsl-function-score-query.html#_boost_factor

[ruflin]

Ok, I see. Looks like we have to do some refactoring of FunctionScore and especially add some tests.

[leabaertschi]

Did you already do something about that? If not I could have a look because I need this quite urgently...

[ruflin]

I will close this one as the pull request is merged and I think it solves this problem.